日期
Dates
模块提供了两种类型来处理日期:Date
和 DateTime
,分别精确到日和毫秒;两者都是抽象类型 TimeType
的子类型。区分类型的动机很简单:不必处理更高精度所带来的复杂性时,一些操作在代码和思维推理上都更加简单。例如,由于 Date
类型仅精确到日(即没有时、分或秒),因此避免了时区、夏令时和闰秒等不必要的通常考虑。
Date
和 DateTime
类型都是基本不可变类型 Int64
的包装类。这两种类型的单个 instant
字段实际上属于 UTInstant{P}
类型。这种类型表示的是一种基于世界时间(UT)持续增长的机器时间 [1]。DateTime
类型并不考虑时区(用 Python 的话讲,它是 naive 的),与 Java 8 中的 LocalDateTime 类似。如果需要附加时区功能,可以通过 TimeZones.jl 包 实现,其汇编了来自 IANA 时区数据库 的数据。Date
和 DateTime
都基于 ISO 8601 标准,遵循公历(格里高利历)。 值得注意的是,ISO 8601 标准对公元前的日期需要特别处理。通常来说,公元前的最后一天是公元前 1 年的 12 月 31 日,接下来的一天是公元 1 年的 1 月 1 日,公元 0 年是不存在的。但是,在 ISO 8601 标准中,公元前 1 年被表示为 0 年,即 0001-01-01
的前一天是 0000-12-31
,而 -0001
(没错,年数为-1)的那一年则实际上是公元前 2 年,-0002
则表示公元前 3 年,以此类推。
构造函数
Date
和 DateTime
类型可以通过整数或 Period
类型,解析,或调整器来构造(稍后会详细介绍):
julia> DateTime(2013)
2013-01-01T00:00:00
julia> DateTime(2013,7)
2013-07-01T00:00:00
julia> DateTime(2013,7,1)
2013-07-01T00:00:00
julia> DateTime(2013,7,1,12)
2013-07-01T12:00:00
julia> DateTime(2013,7,1,12,30)
2013-07-01T12:30:00
julia> DateTime(2013,7,1,12,30,59)
2013-07-01T12:30:59
julia> DateTime(2013,7,1,12,30,59,1)
2013-07-01T12:30:59.001
julia> Date(2013)
2013-01-01
julia> Date(2013,7)
2013-07-01
julia> Date(2013,7,1)
2013-07-01
julia> Date(Dates.Year(2013),Dates.Month(7),Dates.Day(1))
2013-07-01
julia> Date(Dates.Month(7),Dates.Year(2013))
2013-07-01
Date
or DateTime
parsing is accomplished by the use of format strings. Format strings work by the notion of defining delimited or fixed-width "slots" that contain a period to parse and passing the text to parse and format string to a Date
or DateTime
constructor, of the form Date("2015-01-01",dateformat"y-m-d")
or DateTime("20150101",dateformat"yyyymmdd")
.
有分隔的插入点是通过指定解析器在两个时段之间的分隔符来进行标记的。例如,"y-m-d"
会告诉解析器,一个诸如 "2014-07-16"
的时间字符串,应该在第一个和第二个插入点之间查找 -
字符。y
,m
和 d
字符则告诉解析器每一个插入点对应的时段名称。
As in the case of constructors above such as Date(2013)
, delimited DateFormat
s allow for missing parts of dates and times so long as the preceding parts are given. The other parts are given the usual default values. For example, Date("1981-03", dateformat"y-m-d")
returns 1981-03-01
, whilst Date("31/12", dateformat"d/m/y")
gives 0001-12-31
. (Note that the default year is 1 AD/CE.) Consequently, an empty string will always return 0001-01-01
for Date
s, and 0001-01-01T00:00:00.000
for DateTime
s.
Fixed-width slots are specified by repeating the period character the number of times corresponding to the width with no delimiter between characters. So dateformat"yyyymmdd"
would correspond to a date string like "20140716"
. The parser distinguishes a fixed-width slot by the absence of a delimiter, noting the transition "yyyymm"
from one period character to the next.
Support for text-form month parsing is also supported through the u
and U
characters, for abbreviated and full-length month names, respectively. By default, only English month names are supported, so u
corresponds to "Jan", "Feb", "Mar", etc. And U
corresponds to "January", "February", "March", etc. Similar to other name=>value mapping functions dayname
and monthname
, custom locales can be loaded by passing in the locale=>Dict{String,Int}
mapping to the MONTHTOVALUEABBR
and MONTHTOVALUE
dicts for abbreviated and full-name month names, respectively.
The above examples used the dateformat""
string macro. This macro creates a DateFormat
object once when the macro is expanded and uses the same DateFormat
object even if a code snippet is run multiple times.
julia> for i = 1:10^5
Date("2015-01-01", dateformat"y-m-d")
end
Or you can create the DateFormat object explicitly:
julia> df = DateFormat("y-m-d");
julia> dt = Date("2015-01-01",df)
2015-01-01
julia> dt2 = Date("2015-01-02",df)
2015-01-02
Alternatively, use broadcasting:
julia> years = ["2015", "2016"];
julia> Date.(years, DateFormat("yyyy"))
2-element Vector{Date}:
2015-01-01
2016-01-01
For convenience, you may pass the format string directly (e.g., Date("2015-01-01","y-m-d")
), although this form incurs performance costs if you are parsing the same format repeatedly, as it internally creates a new DateFormat
object each time.
As well as via the constructors, a Date
or DateTime
can be constructed from strings using the parse
and tryparse
functions, but with an optional third argument of type DateFormat
specifying the format; for example, parse(Date, "06.23.2013", dateformat"m.d.y")
, or tryparse(DateTime, "1999-12-31T23:59:59")
which uses the default format. The notable difference between the functions is that with tryparse
, an error is not thrown if the string is in an invalid format; instead nothing
is returned. Note however that as with the constructors above, empty date and time parts assume default values and consequently an empty string (""
) is valid for any DateFormat
, giving for example a Date
of 0001-01-01
. Code relying on parse
or tryparse
for Date
and DateTime
parsing should therefore also check whether parsed strings are empty before using the result.
A full suite of parsing and formatting tests and examples is available in stdlib/Dates/test/io.jl
.
Durations/Comparisons
Finding the length of time between two Date
or DateTime
is straightforward given their underlying representation as UTInstant{Day}
and UTInstant{Millisecond}
, respectively. The difference between Date
is returned in the number of Day
, and DateTime
in the number of Millisecond
. Similarly, comparing TimeType
is a simple matter of comparing the underlying machine instants (which in turn compares the internal Int64
values).
julia> dt = Date(2012,2,29)
2012-02-29
julia> dt2 = Date(2000,2,1)
2000-02-01
julia> dump(dt)
Date
instant: Dates.UTInstant{Day}
periods: Day
value: Int64 734562
julia> dump(dt2)
Date
instant: Dates.UTInstant{Day}
periods: Day
value: Int64 730151
julia> dt > dt2
true
julia> dt != dt2
true
julia> dt + dt2
ERROR: MethodError: no method matching +(::Date, ::Date)
[...]
julia> dt * dt2
ERROR: MethodError: no method matching *(::Date, ::Date)
[...]
julia> dt / dt2
ERROR: MethodError: no method matching /(::Date, ::Date)
julia> dt - dt2
4411 days
julia> dt2 - dt
-4411 days
julia> dt = DateTime(2012,2,29)
2012-02-29T00:00:00
julia> dt2 = DateTime(2000,2,1)
2000-02-01T00:00:00
julia> dt - dt2
381110400000 milliseconds
Accessor Functions
Because the Date
and DateTime
types are stored as single Int64
values, date parts or fields can be retrieved through accessor functions. The lowercase accessors return the field as an integer:
julia> t = Date(2014, 1, 31)
2014-01-31
julia> Dates.year(t)
2014
julia> Dates.month(t)
1
julia> Dates.week(t)
5
julia> Dates.day(t)
31
While propercase return the same value in the corresponding Period
type:
julia> Dates.Year(t)
2014 years
julia> Dates.Day(t)
31 days
Compound methods are provided because it is more efficient to access multiple fields at the same time than individually:
julia> Dates.yearmonth(t)
(2014, 1)
julia> Dates.monthday(t)
(1, 31)
julia> Dates.yearmonthday(t)
(2014, 1, 31)
One may also access the underlying UTInstant
or integer value:
julia> dump(t)
Date
instant: Dates.UTInstant{Day}
periods: Day
value: Int64 735264
julia> t.instant
Dates.UTInstant{Day}(Day(735264))
julia> Dates.value(t)
735264
Query Functions
Query functions provide calendrical information about a TimeType
. They include information about the day of the week:
julia> t = Date(2014, 1, 31)
2014-01-31
julia> Dates.dayofweek(t)
5
julia> Dates.dayname(t)
"Friday"
julia> Dates.dayofweekofmonth(t) # 5th Friday of January
5
Month of the year:
julia> Dates.monthname(t)
"January"
julia> Dates.daysinmonth(t)
31
As well as information about the TimeType
's year and quarter:
julia> Dates.isleapyear(t)
false
julia> Dates.dayofyear(t)
31
julia> Dates.quarterofyear(t)
1
julia> Dates.dayofquarter(t)
31
The dayname
and monthname
methods can also take an optional locale
keyword that can be used to return the name of the day or month of the year for other languages/locales. There are also versions of these functions returning the abbreviated names, namely dayabbr
and monthabbr
. First the mapping is loaded into the LOCALES
variable:
julia> french_months = ["janvier", "février", "mars", "avril", "mai", "juin",
"juillet", "août", "septembre", "octobre", "novembre", "décembre"];
julia> french_monts_abbrev = ["janv","févr","mars","avril","mai","juin",
"juil","août","sept","oct","nov","déc"];
julia> french_days = ["lundi","mardi","mercredi","jeudi","vendredi","samedi","dimanche"];
julia> Dates.LOCALES["french"] = Dates.DateLocale(french_months, french_monts_abbrev, french_days, [""]);
The above mentioned functions can then be used to perform the queries:
julia> Dates.dayname(t;locale="french")
"vendredi"
julia> Dates.monthname(t;locale="french")
"janvier"
julia> Dates.monthabbr(t;locale="french")
"janv"
Since the abbreviated versions of the days are not loaded, trying to use the function dayabbr
will error.
julia> Dates.dayabbr(t;locale="french")
ERROR: BoundsError: attempt to access 1-element Vector{String} at index [5]
Stacktrace:
[...]
TimeType-Period Arithmetic
It's good practice when using any language/date framework to be familiar with how date-period arithmetic is handled as there are some tricky issues to deal with (though much less so for day-precision types).
The Dates
module approach tries to follow the simple principle of trying to change as little as possible when doing Period
arithmetic. This approach is also often known as calendrical arithmetic or what you would probably guess if someone were to ask you the same calculation in a conversation. Why all the fuss about this? Let's take a classic example: add 1 month to January 31st, 2014. What's the answer? Javascript will say March 3 (assumes 31 days). PHP says March 2 (assumes 30 days). The fact is, there is no right answer. In the Dates
module, it gives the result of February 28th. How does it figure that out? Consider the classic 7-7-7 gambling game in casinos.
Now just imagine that instead of 7-7-7, the slots are Year-Month-Day, or in our example, 2014-01-31. When you ask to add 1 month to this date, the month slot is incremented, so now we have 2014-02-31. Then the day number is checked if it is greater than the last valid day of the new month; if it is (as in the case above), the day number is adjusted down to the last valid day (28). What are the ramifications with this approach? Go ahead and add another month to our date, 2014-02-28 + Month(1) == 2014-03-28
. What? Were you expecting the last day of March? Nope, sorry, remember the 7-7-7 slots. As few slots as possible are going to change, so we first increment the month slot by 1, 2014-03-28, and boom, we're done because that's a valid date. On the other hand, if we were to add 2 months to our original date, 2014-01-31, then we end up with 2014-03-31, as expected. The other ramification of this approach is a loss in associativity when a specific ordering is forced (i.e. adding things in different orders results in different outcomes). For example:
julia> (Date(2014,1,29)+Dates.Day(1)) + Dates.Month(1)
2014-02-28
julia> (Date(2014,1,29)+Dates.Month(1)) + Dates.Day(1)
2014-03-01
What's going on there? In the first line, we're adding 1 day to January 29th, which results in 2014-01-30; then we add 1 month, so we get 2014-02-30, which then adjusts down to 2014-02-28. In the second example, we add 1 month first, where we get 2014-02-29, which adjusts down to 2014-02-28, and then add 1 day, which results in 2014-03-01. One design principle that helps in this case is that, in the presence of multiple Periods, the operations will be ordered by the Periods' types, not their value or positional order; this means Year
will always be added first, then Month
, then Week
, etc. Hence the following does result in associativity and Just Works:
julia> Date(2014,1,29) + Dates.Day(1) + Dates.Month(1)
2014-03-01
julia> Date(2014,1,29) + Dates.Month(1) + Dates.Day(1)
2014-03-01
Tricky? Perhaps. What is an innocent Dates
user to do? The bottom line is to be aware that explicitly forcing a certain associativity, when dealing with months, may lead to some unexpected results, but otherwise, everything should work as expected. Thankfully, that's pretty much the extent of the odd cases in date-period arithmetic when dealing with time in UT (avoiding the "joys" of dealing with daylight savings, leap seconds, etc.).
As a bonus, all period arithmetic objects work directly with ranges:
julia> dr = Date(2014,1,29):Day(1):Date(2014,2,3)
Date("2014-01-29"):Day(1):Date("2014-02-03")
julia> collect(dr)
6-element Vector{Date}:
2014-01-29
2014-01-30
2014-01-31
2014-02-01
2014-02-02
2014-02-03
julia> dr = Date(2014,1,29):Dates.Month(1):Date(2014,07,29)
Date("2014-01-29"):Month(1):Date("2014-07-29")
julia> collect(dr)
7-element Vector{Date}:
2014-01-29
2014-02-28
2014-03-29
2014-04-29
2014-05-29
2014-06-29
2014-07-29
Adjuster Functions
As convenient as date-period arithmetic is, often the kinds of calculations needed on dates take on a calendrical or temporal nature rather than a fixed number of periods. Holidays are a perfect example; most follow rules such as "Memorial Day = Last Monday of May", or "Thanksgiving = 4th Thursday of November". These kinds of temporal expressions deal with rules relative to the calendar, like first or last of the month, next Tuesday, or the first and third Wednesdays, etc.
The Dates
module provides the adjuster API through several convenient methods that aid in simply and succinctly expressing temporal rules. The first group of adjuster methods deal with the first and last of weeks, months, quarters, and years. They each take a single TimeType
as input and return or adjust to the first or last of the desired period relative to the input.
julia> Dates.firstdayofweek(Date(2014,7,16)) # Adjusts the input to the Monday of the input's week
2014-07-14
julia> Dates.lastdayofmonth(Date(2014,7,16)) # Adjusts to the last day of the input's month
2014-07-31
julia> Dates.lastdayofquarter(Date(2014,7,16)) # Adjusts to the last day of the input's quarter
2014-09-30
The next two higher-order methods, tonext
, and toprev
, generalize working with temporal expressions by taking a DateFunction
as first argument, along with a starting TimeType
. A DateFunction
is just a function, usually anonymous, that takes a single TimeType
as input and returns a Bool
, true
indicating a satisfied adjustment criterion. For example:
julia> istuesday = x->Dates.dayofweek(x) == Dates.Tuesday; # Returns true if the day of the week of x is Tuesday
julia> Dates.tonext(istuesday, Date(2014,7,13)) # 2014-07-13 is a Sunday
2014-07-15
julia> Dates.tonext(Date(2014,7,13), Dates.Tuesday) # Convenience method provided for day of the week adjustments
2014-07-15
This is useful with the do-block syntax for more complex temporal expressions:
julia> Dates.tonext(Date(2014,7,13)) do x
# Return true on the 4th Thursday of November (Thanksgiving)
Dates.dayofweek(x) == Dates.Thursday &&
Dates.dayofweekofmonth(x) == 4 &&
Dates.month(x) == Dates.November
end
2014-11-27
The Base.filter
method can be used to obtain all valid dates/moments in a specified range:
# Pittsburgh street cleaning; Every 2nd Tuesday from April to November
# Date range from January 1st, 2014 to January 1st, 2015
julia> dr = Dates.Date(2014):Day(1):Dates.Date(2015);
julia> filter(dr) do x
Dates.dayofweek(x) == Dates.Tue &&
Dates.April <= Dates.month(x) <= Dates.Nov &&
Dates.dayofweekofmonth(x) == 2
end
8-element Vector{Date}:
2014-04-08
2014-05-13
2014-06-10
2014-07-08
2014-08-12
2014-09-09
2014-10-14
2014-11-11
Additional examples and tests are available in stdlib/Dates/test/adjusters.jl
.
Period Types
Periods are a human view of discrete, sometimes irregular durations of time. Consider 1 month; it could represent, in days, a value of 28, 29, 30, or 31 depending on the year and month context. Or a year could represent 365 or 366 days in the case of a leap year. Period
types are simple Int64
wrappers and are constructed by wrapping any Int64
convertible type, i.e. Year(1)
or Month(3.0)
. Arithmetic between Period
of the same type behave like integers, and limited Period-Real
arithmetic is available. You can extract the underlying integer with Dates.value
.
julia> y1 = Dates.Year(1)
1 year
julia> y2 = Dates.Year(2)
2 years
julia> y3 = Dates.Year(10)
10 years
julia> y1 + y2
3 years
julia> div(y3,y2)
5
julia> y3 - y2
8 years
julia> y3 % y2
0 years
julia> div(y3,3) # mirrors integer division
3 years
julia> Dates.value(Dates.Millisecond(10))
10
Rounding
Date
and DateTime
values can be rounded to a specified resolution (e.g., 1 month or 15 minutes) with floor
, ceil
, or round
:
julia> floor(Date(1985, 8, 16), Dates.Month)
1985-08-01
julia> ceil(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15))
2013-02-13T00:45:00
julia> round(DateTime(2016, 8, 6, 20, 15), Dates.Day)
2016-08-07T00:00:00
Unlike the numeric round
method, which breaks ties toward the even number by default, the TimeType
round
method uses the RoundNearestTiesUp
rounding mode. (It's difficult to guess what breaking ties to nearest "even" TimeType
would entail.) Further details on the available RoundingMode
s can be found in the API reference.
Rounding should generally behave as expected, but there are a few cases in which the expected behaviour is not obvious.
Rounding Epoch
In many cases, the resolution specified for rounding (e.g., Dates.Second(30)
) divides evenly into the next largest period (in this case, Dates.Minute(1)
). But rounding behaviour in cases in which this is not true may lead to confusion. What is the expected result of rounding a DateTime
to the nearest 10 hours?
julia> round(DateTime(2016, 7, 17, 11, 55), Dates.Hour(10))
2016-07-17T12:00:00
That may seem confusing, given that the hour (12) is not divisible by 10. The reason that 2016-07-17T12:00:00
was chosen is that it is 17,676,660 hours after 0000-01-01T00:00:00
, and 17,676,660 is divisible by 10.
As Julia Date
and DateTime
values are represented according to the ISO 8601 standard, 0000-01-01T00:00:00
was chosen as base (or "rounding epoch") from which to begin the count of days (and milliseconds) used in rounding calculations. (Note that this differs slightly from Julia's internal representation of Date
s using Rata Die notation; but since the ISO 8601 standard is most visible to the end user, 0000-01-01T00:00:00
was chosen as the rounding epoch instead of the 0000-12-31T00:00:00
used internally to minimize confusion.)
The only exception to the use of 0000-01-01T00:00:00
as the rounding epoch is when rounding to weeks. Rounding to the nearest week will always return a Monday (the first day of the week as specified by ISO 8601). For this reason, we use 0000-01-03T00:00:00
(the first day of the first week of year 0000, as defined by ISO 8601) as the base when rounding to a number of weeks.
Here is a related case in which the expected behaviour is not necessarily obvious: What happens when we round to the nearest P(2)
, where P
is a Period
type? In some cases (specifically, when P <: Dates.TimePeriod
) the answer is clear:
julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Hour(2))
2016-07-17T08:00:00
julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Minute(2))
2016-07-17T08:56:00
This seems obvious, because two of each of these periods still divides evenly into the next larger order period. But in the case of two months (which still divides evenly into one year), the answer may be surprising:
julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Month(2))
2016-07-01T00:00:00
Why round to the first day in July, even though it is month 7 (an odd number)? The key is that months are 1-indexed (the first month is assigned 1), unlike hours, minutes, seconds, and milliseconds (the first of which are assigned 0).
This means that rounding a DateTime
to an even multiple of seconds, minutes, hours, or years (because the ISO 8601 specification includes a year zero) will result in a DateTime
with an even value in that field, while rounding a DateTime
to an even multiple of months will result in the months field having an odd value. Because both months and years may contain an irregular number of days, whether rounding to an even number of days will result in an even value in the days field is uncertain.
See the API reference for additional information on methods exported from the Dates
module.
API reference
Dates and Time Types
Dates.Period
— TypePeriod
Year
Quarter
Month
Week
Day
Hour
Minute
Second
Millisecond
Microsecond
Nanosecond
Period
types represent discrete, human representations of time.
Dates.CompoundPeriod
— TypeCompoundPeriod
A CompoundPeriod
is useful for expressing time periods that are not a fixed multiple of smaller periods. For example, "a year and a day" is not a fixed number of days, but can be expressed using a CompoundPeriod
. In fact, a CompoundPeriod
is automatically generated by addition of different period types, e.g. Year(1) + Day(1)
produces a CompoundPeriod
result.
Dates.Instant
— TypeInstant
Instant
types represent integer-based, machine representations of time as continuous timelines starting from an epoch.
Dates.UTInstant
— TypeUTInstant{T}
The UTInstant
represents a machine timeline based on UT time (1 day = one revolution of the earth). The T
is a Period
parameter that indicates the resolution or precision of the instant.
Dates.TimeType
— TypeTimeType
TimeType
types wrap Instant
machine instances to provide human representations of the machine instant. Time
, DateTime
and Date
are subtypes of TimeType
.
Dates.DateTime
— TypeDateTime
DateTime
wraps a UTInstant{Millisecond}
and interprets it according to the proleptic Gregorian calendar.
Dates.Date
— TypeDate
Date
wraps a UTInstant{Day}
and interprets it according to the proleptic Gregorian calendar.
Dates.Time
— TypeTime
Time
wraps a Nanosecond
and represents a specific moment in a 24-hour day.
Dates.TimeZone
— TypeTimeZone
Geographic zone generally based on longitude determining what the time is at a certain location. Some time zones observe daylight savings (eg EST -> EDT). For implementations and more support, see the TimeZones.jl
package
Dates.UTC
— TypeUTC
UTC
, or Coordinated Universal Time, is the TimeZone
from which all others are measured. It is associated with the time at 0° longitude. It is not adjusted for daylight savings.
Dates Functions
Dates.DateTime
— MethodDateTime(y, [m, d, h, mi, s, ms]) -> DateTime
Construct a DateTime
type by parts. Arguments must be convertible to Int64
.
Dates.DateTime
— MethodDateTime(periods::Period...) -> DateTime
Construct a DateTime
type by Period
type parts. Arguments may be in any order. DateTime parts not provided will default to the value of Dates.default(period)
.
Dates.DateTime
— MethodDateTime(f::Function, y[, m, d, h, mi, s]; step=Day(1), limit=10000) -> DateTime
Create a DateTime
through the adjuster API. The starting point will be constructed from the provided y, m, d...
arguments, and will be adjusted until f::Function
returns true
. The step size in adjusting can be provided manually through the step
keyword. limit
provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (in the case that f::Function
is never satisfied).
Examples
julia> DateTime(dt -> Dates.second(dt) == 40, 2010, 10, 20, 10; step = Dates.Second(1))
2010-10-20T10:00:40
julia> DateTime(dt -> Dates.hour(dt) == 20, 2010, 10, 20, 10; step = Dates.Hour(1), limit = 5)
ERROR: ArgumentError: Adjustment limit reached: 5 iterations
Stacktrace:
[...]
Dates.DateTime
— MethodDateTime(dt::Date) -> DateTime
Convert a Date
to a DateTime
. The hour, minute, second, and millisecond parts of the new DateTime
are assumed to be zero.
Dates.DateTime
— MethodDateTime(dt::AbstractString, format::AbstractString; locale="english") -> DateTime
Construct a DateTime
by parsing the dt
date time string following the pattern given in the format
string (see DateFormat
for syntax).
This method creates a DateFormat
object each time it is called. It is recommended that you create a DateFormat
object instead and use that as the second argument to avoid performance loss when using the same format repeatedly.
Example
julia> DateTime("2020-01-01", "yyyy-mm-dd")
2020-01-01T00:00:00
julia> a = ("2020-01-01", "2020-01-02");
julia> [DateTime(d, dateformat"yyyy-mm-dd") for d ∈ a] # preferred
2-element Vector{DateTime}:
2020-01-01T00:00:00
2020-01-02T00:00:00
Dates.format
— Methodformat(dt::TimeType, format::AbstractString; locale="english") -> AbstractString
Construct a string by using a TimeType
object and applying the provided format
. The following character codes can be used to construct the format
string:
Code | Examples | Comment |
---|---|---|
y | 6 | Numeric year with a fixed width |
Y | 1996 | Numeric year with a minimum width |
m | 1, 12 | Numeric month with a minimum width |
u | Jan | Month name shortened to 3-chars according to the locale |
U | January | Full month name according to the locale keyword |
d | 1, 31 | Day of the month with a minimum width |
H | 0, 23 | Hour (24-hour clock) with a minimum width |
M | 0, 59 | Minute with a minimum width |
S | 0, 59 | Second with a minimum width |
s | 000, 500 | Millisecond with a minimum width of 3 |
e | Mon, Tue | Abbreviated days of the week |
E | Monday | Full day of week name |
The number of sequential code characters indicate the width of the code. A format of yyyy-mm
specifies that the code y
should have a width of four while m
a width of two. Codes that yield numeric digits have an associated mode: fixed-width or minimum-width. The fixed-width mode left-pads the value with zeros when it is shorter than the specified width and truncates the value when longer. Minimum-width mode works the same as fixed-width except that it does not truncate values longer than the width.
When creating a format
you can use any non-code characters as a separator. For example to generate the string "1996-01-15T00:00:00" you could use format
: "yyyy-mm-ddTHH:MM:SS". Note that if you need to use a code character as a literal you can use the escape character backslash. The string "1996y01m" can be produced with the format "yyyy\ymm\m".
Dates.DateFormat
— TypeDateFormat(format::AbstractString, locale="english") -> DateFormat
Construct a date formatting object that can be used for parsing date strings or formatting a date object as a string. The following character codes can be used to construct the format
string:
Code | Matches | Comment |
---|---|---|
y | 1996, 96 | Returns year of 1996, 0096 |
Y | 1996, 96 | Returns year of 1996, 0096. Equivalent to y |
m | 1, 01 | Matches 1 or 2-digit months |
u | Jan | Matches abbreviated months according to the locale keyword |
U | January | Matches full month names according to the locale keyword |
d | 1, 01 | Matches 1 or 2-digit days |
H | 00 | Matches hours (24-hour clock) |
I | 00 | For outputting hours with 12-hour clock |
M | 00 | Matches minutes |
S | 00 | Matches seconds |
s | .500 | Matches milliseconds |
e | Mon, Tues | Matches abbreviated days of the week |
E | Monday | Matches full name days of the week |
p | AM | Matches AM/PM (case-insensitive) |
yyyymmdd | 19960101 | Matches fixed-width year, month, and day |
Characters not listed above are normally treated as delimiters between date and time slots. For example a dt
string of "1996-01-15T00:00:00.0" would have a format
string like "y-m-dTH:M:S.s". If you need to use a code character as a delimiter you can escape it using backslash. The date "1995y01m" would have the format "y\ym\m".
Note that 12:00AM corresponds 00:00 (midnight), and 12:00PM corresponds to 12:00 (noon). When parsing a time with a p
specifier, any hour (either H
or I
) is interpreted as as a 12-hour clock, so the I
code is mainly useful for output.
Creating a DateFormat object is expensive. Whenever possible, create it once and use it many times or try the dateformat""
string macro. Using this macro creates the DateFormat object once at macro expansion time and reuses it later. There are also several pre-defined formatters, listed later.
See DateTime
and format
for how to use a DateFormat object to parse and write Date strings respectively.
Dates.@dateformat_str
— Macrodateformat"Y-m-d H:M:S"
Create a DateFormat
object. Similar to DateFormat("Y-m-d H:M:S")
but creates the DateFormat object once during macro expansion.
See DateFormat
for details about format specifiers.
Dates.DateTime
— MethodDateTime(dt::AbstractString, df::DateFormat=ISODateTimeFormat) -> DateTime
Construct a DateTime
by parsing the dt
date time string following the pattern given in the DateFormat
object, or dateformat"yyyy-mm-ddTHH:MM:SS.s" if omitted.
Similar to DateTime(::AbstractString, ::AbstractString)
but more efficient when repeatedly parsing similarly formatted date time strings with a pre-created DateFormat
object.
Dates.Date
— MethodDate(y, [m, d]) -> Date
Construct a Date
type by parts. Arguments must be convertible to Int64
.
Dates.Date
— MethodDate(period::Period...) -> Date
Construct a Date
type by Period
type parts. Arguments may be in any order. Date
parts not provided will default to the value of Dates.default(period)
.
Dates.Date
— MethodDate(f::Function, y[, m, d]; step=Day(1), limit=10000) -> Date
Create a Date
through the adjuster API. The starting point will be constructed from the provided y, m, d
arguments, and will be adjusted until f::Function
returns true
. The step size in adjusting can be provided manually through the step
keyword. limit
provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (given that f::Function
is never satisfied).
Examples
julia> Date(date -> Dates.week(date) == 20, 2010, 01, 01)
2010-05-17
julia> Date(date -> Dates.year(date) == 2010, 2000, 01, 01)
2010-01-01
julia> Date(date -> Dates.month(date) == 10, 2000, 01, 01; limit = 5)
ERROR: ArgumentError: Adjustment limit reached: 5 iterations
Stacktrace:
[...]
Dates.Date
— MethodDate(dt::DateTime) -> Date
Convert a DateTime
to a Date
. The hour, minute, second, and millisecond parts of the DateTime
are truncated, so only the year, month and day parts are used in construction.
Dates.Date
— MethodDate(d::AbstractString, format::AbstractString; locale="english") -> Date
Construct a Date
by parsing the d
date string following the pattern given in the format
string (see DateFormat
for syntax).
This method creates a DateFormat
object each time it is called. It is recommended that you create a DateFormat
object instead and use that as the second argument to avoid performance loss when using the same format repeatedly.
Example
julia> Date("2020-01-01", "yyyy-mm-dd")
2020-01-01
julia> a = ("2020-01-01", "2020-01-02");
julia> [Date(d, dateformat"yyyy-mm-dd") for d ∈ a] # preferred
2-element Vector{Date}:
2020-01-01
2020-01-02
Dates.Date
— MethodDate(d::AbstractString, df::DateFormat=ISODateFormat) -> Date
Construct a Date
by parsing the d
date string following the pattern given in the DateFormat
object, or dateformat"yyyy-mm-dd" if omitted.
Similar to Date(::AbstractString, ::AbstractString)
but more efficient when repeatedly parsing similarly formatted date strings with a pre-created DateFormat
object.
Dates.Time
— MethodTime(h, [mi, s, ms, us, ns]) -> Time
Construct a Time
type by parts. Arguments must be convertible to Int64
.
Dates.Time
— MethodTime(period::TimePeriod...) -> Time
Construct a Time
type by Period
type parts. Arguments may be in any order. Time
parts not provided will default to the value of Dates.default(period)
.
Dates.Time
— MethodTime(f::Function, h, mi=0; step::Period=Second(1), limit::Int=10000)
Time(f::Function, h, mi, s; step::Period=Millisecond(1), limit::Int=10000)
Time(f::Function, h, mi, s, ms; step::Period=Microsecond(1), limit::Int=10000)
Time(f::Function, h, mi, s, ms, us; step::Period=Nanosecond(1), limit::Int=10000)
Create a Time
through the adjuster API. The starting point will be constructed from the provided h, mi, s, ms, us
arguments, and will be adjusted until f::Function
returns true
. The step size in adjusting can be provided manually through the step
keyword. limit
provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (in the case that f::Function
is never satisfied). Note that the default step will adjust to allow for greater precision for the given arguments; i.e. if hour, minute, and second arguments are provided, the default step will be Millisecond(1)
instead of Second(1)
.
Examples
julia> Dates.Time(t -> Dates.minute(t) == 30, 20)
20:30:00
julia> Dates.Time(t -> Dates.minute(t) == 0, 20)
20:00:00
julia> Dates.Time(t -> Dates.hour(t) == 10, 3; limit = 5)
ERROR: ArgumentError: Adjustment limit reached: 5 iterations
Stacktrace:
[...]
Dates.Time
— MethodTime(dt::DateTime) -> Time
Convert a DateTime
to a Time
. The hour, minute, second, and millisecond parts of the DateTime
are used to create the new Time
. Microsecond and nanoseconds are zero by default.
Dates.Time
— MethodTime(t::AbstractString, format::AbstractString; locale="english") -> Time
Construct a Time
by parsing the t
time string following the pattern given in the format
string (see DateFormat
for syntax).
This method creates a DateFormat
object each time it is called. It is recommended that you create a DateFormat
object instead and use that as the second argument to avoid performance loss when using the same format repeatedly.
Example
julia> Time("12:34pm", "HH:MMp")
12:34:00
julia> a = ("12:34pm", "2:34am");
julia> [Time(d, dateformat"HH:MMp") for d ∈ a] # preferred
2-element Vector{Time}:
12:34:00
02:34:00
Dates.Time
— MethodTime(t::AbstractString, df::DateFormat=ISOTimeFormat) -> Time
Construct a Time
by parsing the t
date time string following the pattern given in the DateFormat
object, or dateformat"HH:MM:SS.s" if omitted.
Similar to Time(::AbstractString, ::AbstractString)
but more efficient when repeatedly parsing similarly formatted time strings with a pre-created DateFormat
object.
Dates.now
— Methodnow() -> DateTime
Return a DateTime
corresponding to the user's system time including the system timezone locale.
Dates.now
— Methodnow(::Type{UTC}) -> DateTime
Return a DateTime
corresponding to the user's system time as UTC/GMT.
Base.eps
— Methodeps(::Type{DateTime}) -> Millisecond
eps(::Type{Date}) -> Day
eps(::Type{Time}) -> Nanosecond
eps(::TimeType) -> Period
Return the smallest unit value supported by the TimeType
.
Examples
julia> eps(DateTime)
1 millisecond
julia> eps(Date)
1 day
julia> eps(Time)
1 nanosecond
Accessor Functions
Dates.year
— Functionyear(dt::TimeType) -> Int64
The year of a Date
or DateTime
as an Int64
.
Dates.month
— Functionmonth(dt::TimeType) -> Int64
The month of a Date
or DateTime
as an Int64
.
Dates.week
— Functionweek(dt::TimeType) -> Int64
Return the ISO week date of a Date
or DateTime
as an Int64
. Note that the first week of a year is the week that contains the first Thursday of the year, which can result in dates prior to January 4th being in the last week of the previous year. For example, week(Date(2005, 1, 1))
is the 53rd week of 2004.
Examples
julia> Dates.week(Date(1989, 6, 22))
25
julia> Dates.week(Date(2005, 1, 1))
53
julia> Dates.week(Date(2004, 12, 31))
53
Dates.day
— Functionday(dt::TimeType) -> Int64
The day of month of a Date
or DateTime
as an Int64
.
Dates.hour
— Functionhour(dt::DateTime) -> Int64
The hour of day of a DateTime
as an Int64
.
hour(t::Time) -> Int64
The hour of a Time
as an Int64
.
Dates.minute
— Functionminute(dt::DateTime) -> Int64
The minute of a DateTime
as an Int64
.
minute(t::Time) -> Int64
The minute of a Time
as an Int64
.
Dates.second
— Functionsecond(dt::DateTime) -> Int64
The second of a DateTime
as an Int64
.
second(t::Time) -> Int64
The second of a Time
as an Int64
.
Dates.millisecond
— Functionmillisecond(dt::DateTime) -> Int64
The millisecond of a DateTime
as an Int64
.
millisecond(t::Time) -> Int64
The millisecond of a Time
as an Int64
.
Dates.microsecond
— Functionmicrosecond(t::Time) -> Int64
The microsecond of a Time
as an Int64
.
Dates.nanosecond
— Functionnanosecond(t::Time) -> Int64
The nanosecond of a Time
as an Int64
.
Dates.Year
— MethodYear(v)
Construct a Year
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Month
— MethodMonth(v)
Construct a Month
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Week
— MethodWeek(v)
Construct a Week
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Day
— MethodDay(v)
Construct a Day
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Hour
— MethodHour(dt::DateTime) -> Hour
The hour part of a DateTime as a Hour
.
Dates.Minute
— MethodMinute(dt::DateTime) -> Minute
The minute part of a DateTime as a Minute
.
Dates.Second
— MethodSecond(dt::DateTime) -> Second
The second part of a DateTime as a Second
.
Dates.Millisecond
— MethodMillisecond(dt::DateTime) -> Millisecond
The millisecond part of a DateTime as a Millisecond
.
Dates.Microsecond
— MethodMicrosecond(dt::Time) -> Microsecond
The microsecond part of a Time as a Microsecond
.
Dates.Nanosecond
— MethodNanosecond(dt::Time) -> Nanosecond
The nanosecond part of a Time as a Nanosecond
.
Dates.yearmonth
— Functionyearmonth(dt::TimeType) -> (Int64, Int64)
Simultaneously return the year and month parts of a Date
or DateTime
.
Dates.monthday
— Functionmonthday(dt::TimeType) -> (Int64, Int64)
Simultaneously return the month and day parts of a Date
or DateTime
.
Dates.yearmonthday
— Functionyearmonthday(dt::TimeType) -> (Int64, Int64, Int64)
Simultaneously return the year, month and day parts of a Date
or DateTime
.
Query Functions
Dates.dayname
— Functiondayname(dt::TimeType; locale="english") -> String
dayname(day::Integer; locale="english") -> String
Return the full day name corresponding to the day of the week of the Date
or DateTime
in the given locale
. Also accepts Integer
.
Examples
julia> Dates.dayname(Date("2000-01-01"))
"Saturday"
julia> Dates.dayname(4)
"Thursday"
Dates.dayabbr
— Functiondayabbr(dt::TimeType; locale="english") -> String
dayabbr(day::Integer; locale="english") -> String
Return the abbreviated name corresponding to the day of the week of the Date
or DateTime
in the given locale
. Also accepts Integer
.
Examples
julia> Dates.dayabbr(Date("2000-01-01"))
"Sat"
julia> Dates.dayabbr(3)
"Wed"
Dates.dayofweek
— Functiondayofweek(dt::TimeType) -> Int64
Return the day of the week as an Int64
with 1 = Monday, 2 = Tuesday, etc.
.
Examples
julia> Dates.dayofweek(Date("2000-01-01"))
6
Dates.dayofmonth
— Functiondayofmonth(dt::TimeType) -> Int64
The day of month of a Date
or DateTime
as an Int64
.
Dates.dayofweekofmonth
— Functiondayofweekofmonth(dt::TimeType) -> Int
For the day of week of dt
, return which number it is in dt
's month. So if the day of the week of dt
is Monday, then 1 = First Monday of the month, 2 = Second Monday of the month, etc.
In the range 1:5.
Examples
julia> Dates.dayofweekofmonth(Date("2000-02-01"))
1
julia> Dates.dayofweekofmonth(Date("2000-02-08"))
2
julia> Dates.dayofweekofmonth(Date("2000-02-15"))
3
Dates.daysofweekinmonth
— Functiondaysofweekinmonth(dt::TimeType) -> Int
For the day of week of dt
, return the total number of that day of the week in dt
's month. Returns 4 or 5. Useful in temporal expressions for specifying the last day of a week in a month by including dayofweekofmonth(dt) == daysofweekinmonth(dt)
in the adjuster function.
Examples
julia> Dates.daysofweekinmonth(Date("2005-01-01"))
5
julia> Dates.daysofweekinmonth(Date("2005-01-04"))
4
Dates.monthname
— Functionmonthname(dt::TimeType; locale="english") -> String
monthname(month::Integer, locale="english") -> String
Return the full name of the month of the Date
or DateTime
or Integer
in the given locale
.
Examples
julia> Dates.monthname(Date("2005-01-04"))
"January"
julia> Dates.monthname(2)
"February"
Dates.monthabbr
— Functionmonthabbr(dt::TimeType; locale="english") -> String
monthabbr(month::Integer, locale="english") -> String
Return the abbreviated month name of the Date
or DateTime
or Integer
in the given locale
.
Examples
julia> Dates.monthabbr(Date("2005-01-04"))
"Jan"
julia> monthabbr(2)
"Feb"
Dates.daysinmonth
— Functiondaysinmonth(dt::TimeType) -> Int
Return the number of days in the month of dt
. Value will be 28, 29, 30, or 31.
Examples
julia> Dates.daysinmonth(Date("2000-01"))
31
julia> Dates.daysinmonth(Date("2001-02"))
28
julia> Dates.daysinmonth(Date("2000-02"))
29
Dates.isleapyear
— Functionisleapyear(dt::TimeType) -> Bool
Return true
if the year of dt
is a leap year.
Examples
julia> Dates.isleapyear(Date("2004"))
true
julia> Dates.isleapyear(Date("2005"))
false
Dates.dayofyear
— Functiondayofyear(dt::TimeType) -> Int
Return the day of the year for dt
with January 1st being day 1.
Dates.daysinyear
— Functiondaysinyear(dt::TimeType) -> Int
Return 366 if the year of dt
is a leap year, otherwise return 365.
Examples
julia> Dates.daysinyear(1999)
365
julia> Dates.daysinyear(2000)
366
Dates.quarterofyear
— Functionquarterofyear(dt::TimeType) -> Int
Return the quarter that dt
resides in. Range of value is 1:4.
Dates.dayofquarter
— Functiondayofquarter(dt::TimeType) -> Int
Return the day of the current quarter of dt
. Range of value is 1:92.
Adjuster Functions
Base.trunc
— Methodtrunc(dt::TimeType, ::Type{Period}) -> TimeType
Truncates the value of dt
according to the provided Period
type.
Examples
julia> trunc(Dates.DateTime("1996-01-01T12:30:00"), Dates.Day)
1996-01-01T00:00:00
Dates.firstdayofweek
— Functionfirstdayofweek(dt::TimeType) -> TimeType
Adjusts dt
to the Monday of its week.
Examples
julia> Dates.firstdayofweek(DateTime("1996-01-05T12:30:00"))
1996-01-01T00:00:00
Dates.lastdayofweek
— Functionlastdayofweek(dt::TimeType) -> TimeType
Adjusts dt
to the Sunday of its week.
Examples
julia> Dates.lastdayofweek(DateTime("1996-01-05T12:30:00"))
1996-01-07T00:00:00
Dates.firstdayofmonth
— Functionfirstdayofmonth(dt::TimeType) -> TimeType
Adjusts dt
to the first day of its month.
Examples
julia> Dates.firstdayofmonth(DateTime("1996-05-20"))
1996-05-01T00:00:00
Dates.lastdayofmonth
— Functionlastdayofmonth(dt::TimeType) -> TimeType
Adjusts dt
to the last day of its month.
Examples
julia> Dates.lastdayofmonth(DateTime("1996-05-20"))
1996-05-31T00:00:00
Dates.firstdayofyear
— Functionfirstdayofyear(dt::TimeType) -> TimeType
Adjusts dt
to the first day of its year.
Examples
julia> Dates.firstdayofyear(DateTime("1996-05-20"))
1996-01-01T00:00:00
Dates.lastdayofyear
— Functionlastdayofyear(dt::TimeType) -> TimeType
Adjusts dt
to the last day of its year.
Examples
julia> Dates.lastdayofyear(DateTime("1996-05-20"))
1996-12-31T00:00:00
Dates.firstdayofquarter
— Functionfirstdayofquarter(dt::TimeType) -> TimeType
Adjusts dt
to the first day of its quarter.
Examples
julia> Dates.firstdayofquarter(DateTime("1996-05-20"))
1996-04-01T00:00:00
julia> Dates.firstdayofquarter(DateTime("1996-08-20"))
1996-07-01T00:00:00
Dates.lastdayofquarter
— Functionlastdayofquarter(dt::TimeType) -> TimeType
Adjusts dt
to the last day of its quarter.
Examples
julia> Dates.lastdayofquarter(DateTime("1996-05-20"))
1996-06-30T00:00:00
julia> Dates.lastdayofquarter(DateTime("1996-08-20"))
1996-09-30T00:00:00
Dates.tonext
— Methodtonext(dt::TimeType, dow::Int; same::Bool=false) -> TimeType
Adjusts dt
to the next day of week corresponding to dow
with 1 = Monday, 2 = Tuesday, etc
. Setting same=true
allows the current dt
to be considered as the next dow
, allowing for no adjustment to occur.
Dates.toprev
— Methodtoprev(dt::TimeType, dow::Int; same::Bool=false) -> TimeType
Adjusts dt
to the previous day of week corresponding to dow
with 1 = Monday, 2 = Tuesday, etc
. Setting same=true
allows the current dt
to be considered as the previous dow
, allowing for no adjustment to occur.
Dates.tofirst
— Functiontofirst(dt::TimeType, dow::Int; of=Month) -> TimeType
Adjusts dt
to the first dow
of its month. Alternatively, of=Year
will adjust to the first dow
of the year.
Dates.tolast
— Functiontolast(dt::TimeType, dow::Int; of=Month) -> TimeType
Adjusts dt
to the last dow
of its month. Alternatively, of=Year
will adjust to the last dow
of the year.
Dates.tonext
— Methodtonext(func::Function, dt::TimeType; step=Day(1), limit=10000, same=false) -> TimeType
Adjusts dt
by iterating at most limit
iterations by step
increments until func
returns true
. func
must take a single TimeType
argument and return a Bool
. same
allows dt
to be considered in satisfying func
.
Dates.toprev
— Methodtoprev(func::Function, dt::TimeType; step=Day(-1), limit=10000, same=false) -> TimeType
Adjusts dt
by iterating at most limit
iterations by step
increments until func
returns true
. func
must take a single TimeType
argument and return a Bool
. same
allows dt
to be considered in satisfying func
.
Periods
Dates.Period
— MethodYear(v)
Quarter(v)
Month(v)
Week(v)
Day(v)
Hour(v)
Minute(v)
Second(v)
Millisecond(v)
Microsecond(v)
Nanosecond(v)
Construct a Period
type with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.CompoundPeriod
— MethodCompoundPeriod(periods) -> CompoundPeriod
Construct a CompoundPeriod
from a Vector
of Period
s. All Period
s of the same type will be added together.
Examples
julia> Dates.CompoundPeriod(Dates.Hour(12), Dates.Hour(13))
25 hours
julia> Dates.CompoundPeriod(Dates.Hour(-1), Dates.Minute(1))
-1 hour, 1 minute
julia> Dates.CompoundPeriod(Dates.Month(1), Dates.Week(-2))
1 month, -2 weeks
julia> Dates.CompoundPeriod(Dates.Minute(50000))
50000 minutes
Dates.value
— FunctionDates.value(x::Period) -> Int64
For a given period, return the value associated with that period. For example, value(Millisecond(10))
returns 10 as an integer.
Dates.default
— Functiondefault(p::Period) -> Period
Returns a sensible "default" value for the input Period by returning T(1)
for Year, Month, and Day, and T(0)
for Hour, Minute, Second, and Millisecond.
Dates.periods
— FunctionDates.periods(::CompoundPeriod) -> Vector{Period}
Return the Vector
of Period
s that comprise the given CompoundPeriod
.
This function requires Julia 1.7 or later.
Rounding Functions
Date
and DateTime
values can be rounded to a specified resolution (e.g., 1 month or 15 minutes) with floor
, ceil
, or round
.
Base.floor
— Methodfloor(dt::TimeType, p::Period) -> TimeType
Return the nearest Date
or DateTime
less than or equal to dt
at resolution p
.
For convenience, p
may be a type instead of a value: floor(dt, Dates.Hour)
is a shortcut for floor(dt, Dates.Hour(1))
.
julia> floor(Date(1985, 8, 16), Dates.Month)
1985-08-01
julia> floor(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15))
2013-02-13T00:30:00
julia> floor(DateTime(2016, 8, 6, 12, 0, 0), Dates.Day)
2016-08-06T00:00:00
Base.ceil
— Methodceil(dt::TimeType, p::Period) -> TimeType
Return the nearest Date
or DateTime
greater than or equal to dt
at resolution p
.
For convenience, p
may be a type instead of a value: ceil(dt, Dates.Hour)
is a shortcut for ceil(dt, Dates.Hour(1))
.
julia> ceil(Date(1985, 8, 16), Dates.Month)
1985-09-01
julia> ceil(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15))
2013-02-13T00:45:00
julia> ceil(DateTime(2016, 8, 6, 12, 0, 0), Dates.Day)
2016-08-07T00:00:00
Base.round
— Methodround(dt::TimeType, p::Period, [r::RoundingMode]) -> TimeType
Return the Date
or DateTime
nearest to dt
at resolution p
. By default (RoundNearestTiesUp
), ties (e.g., rounding 9:30 to the nearest hour) will be rounded up.
For convenience, p
may be a type instead of a value: round(dt, Dates.Hour)
is a shortcut for round(dt, Dates.Hour(1))
.
julia> round(Date(1985, 8, 16), Dates.Month)
1985-08-01
julia> round(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15))
2013-02-13T00:30:00
julia> round(DateTime(2016, 8, 6, 12, 0, 0), Dates.Day)
2016-08-07T00:00:00
Valid rounding modes for round(::TimeType, ::Period, ::RoundingMode)
are RoundNearestTiesUp
(default), RoundDown
(floor
), and RoundUp
(ceil
).
Most Period
values can also be rounded to a specified resolution:
Base.floor
— Methodfloor(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} -> T
Round x
down to the nearest multiple of precision
. If x
and precision
are different subtypes of Period
, the return value will have the same type as precision
.
For convenience, precision
may be a type instead of a value: floor(x, Dates.Hour)
is a shortcut for floor(x, Dates.Hour(1))
.
julia> floor(Dates.Day(16), Dates.Week)
2 weeks
julia> floor(Dates.Minute(44), Dates.Minute(15))
30 minutes
julia> floor(Dates.Hour(36), Dates.Day)
1 day
Rounding to a precision
of Month
s or Year
s is not supported, as these Period
s are of inconsistent length.
Base.ceil
— Methodceil(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} -> T
Round x
up to the nearest multiple of precision
. If x
and precision
are different subtypes of Period
, the return value will have the same type as precision
.
For convenience, precision
may be a type instead of a value: ceil(x, Dates.Hour)
is a shortcut for ceil(x, Dates.Hour(1))
.
julia> ceil(Dates.Day(16), Dates.Week)
3 weeks
julia> ceil(Dates.Minute(44), Dates.Minute(15))
45 minutes
julia> ceil(Dates.Hour(36), Dates.Day)
2 days
Rounding to a precision
of Month
s or Year
s is not supported, as these Period
s are of inconsistent length.
Base.round
— Methodround(x::Period, precision::T, [r::RoundingMode]) where T <: Union{TimePeriod, Week, Day} -> T
Round x
to the nearest multiple of precision
. If x
and precision
are different subtypes of Period
, the return value will have the same type as precision
. By default (RoundNearestTiesUp
), ties (e.g., rounding 90 minutes to the nearest hour) will be rounded up.
For convenience, precision
may be a type instead of a value: round(x, Dates.Hour)
is a shortcut for round(x, Dates.Hour(1))
.
julia> round(Dates.Day(16), Dates.Week)
2 weeks
julia> round(Dates.Minute(44), Dates.Minute(15))
45 minutes
julia> round(Dates.Hour(36), Dates.Day)
2 days
Valid rounding modes for round(::Period, ::T, ::RoundingMode)
are RoundNearestTiesUp
(default), RoundDown
(floor
), and RoundUp
(ceil
).
Rounding to a precision
of Month
s or Year
s is not supported, as these Period
s are of inconsistent length.
The following functions are not exported:
Dates.floorceil
— Functionfloorceil(dt::TimeType, p::Period) -> (TimeType, TimeType)
Simultaneously return the floor
and ceil
of a Date
or DateTime
at resolution p
. More efficient than calling both floor
and ceil
individually.
floorceil(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} -> (T, T)
Simultaneously return the floor
and ceil
of Period
at resolution p
. More efficient than calling both floor
and ceil
individually.
Dates.epochdays2date
— Functionepochdays2date(days) -> Date
Take the number of days since the rounding epoch (0000-01-01T00:00:00
) and return the corresponding Date
.
Dates.epochms2datetime
— Functionepochms2datetime(milliseconds) -> DateTime
Take the number of milliseconds since the rounding epoch (0000-01-01T00:00:00
) and return the corresponding DateTime
.
Dates.date2epochdays
— Functiondate2epochdays(dt::Date) -> Int64
Take the given Date
and return the number of days since the rounding epoch (0000-01-01T00:00:00
) as an Int64
.
Dates.datetime2epochms
— Functiondatetime2epochms(dt::DateTime) -> Int64
Take the given DateTime
and return the number of milliseconds since the rounding epoch (0000-01-01T00:00:00
) as an Int64
.
Conversion Functions
Dates.today
— Functiontoday() -> Date
Return the date portion of now()
.
Dates.unix2datetime
— Functionunix2datetime(x) -> DateTime
Take the number of seconds since unix epoch 1970-01-01T00:00:00
and convert to the corresponding DateTime
.
Dates.datetime2unix
— Functiondatetime2unix(dt::DateTime) -> Float64
Take the given DateTime
and return the number of seconds since the unix epoch 1970-01-01T00:00:00
as a Float64
.
Dates.julian2datetime
— Functionjulian2datetime(julian_days) -> DateTime
Take the number of Julian calendar days since epoch -4713-11-24T12:00:00
and return the corresponding DateTime
.
Dates.datetime2julian
— Functiondatetime2julian(dt::DateTime) -> Float64
Take the given DateTime
and return the number of Julian calendar days since the julian epoch -4713-11-24T12:00:00
as a Float64
.
Dates.rata2datetime
— Functionrata2datetime(days) -> DateTime
Take the number of Rata Die days since epoch 0000-12-31T00:00:00
and return the corresponding DateTime
.
Dates.datetime2rata
— Functiondatetime2rata(dt::TimeType) -> Int64
Return the number of Rata Die days since epoch from the given Date
or DateTime
.
Constants
Days of the Week:
Variable | Abbr. | Value (Int) |
---|---|---|
Monday | Mon | 1 |
Tuesday | Tue | 2 |
Wednesday | Wed | 3 |
Thursday | Thu | 4 |
Friday | Fri | 5 |
Saturday | Sat | 6 |
Sunday | Sun | 7 |
Months of the Year:
Variable | Abbr. | Value (Int) |
---|---|---|
January | Jan | 1 |
February | Feb | 2 |
March | Mar | 3 |
April | Apr | 4 |
May | May | 5 |
June | Jun | 6 |
July | Jul | 7 |
August | Aug | 8 |
September | Sep | 9 |
October | Oct | 10 |
November | Nov | 11 |
December | Dec | 12 |
Common Date Formatters
Dates.ISODateTimeFormat
— ConstantDates.ISODateTimeFormat
Describes the ISO8601 formatting for a date and time. This is the default value for Dates.format
of a DateTime
.
Example
julia> Dates.format(DateTime(2018, 8, 8, 12, 0, 43, 1), ISODateTimeFormat)
"2018-08-08T12:00:43.001"
Dates.ISODateFormat
— ConstantDates.ISODateFormat
Describes the ISO8601 formatting for a date. This is the default value for Dates.format
of a Date
.
Example
julia> Dates.format(Date(2018, 8, 8), ISODateFormat)
"2018-08-08"
Dates.ISOTimeFormat
— ConstantDates.ISOTimeFormat
Describes the ISO8601 formatting for a time. This is the default value for Dates.format
of a Time
.
Example
julia> Dates.format(Time(12, 0, 43, 1), ISOTimeFormat)
"12:00:43.001"
Dates.RFC1123Format
— ConstantDates.RFC1123Format
Describes the RFC1123 formatting for a date and time.
Example
julia> Dates.format(DateTime(2018, 8, 8, 12, 0, 43, 1), RFC1123Format)
"Wed, 08 Aug 2018 12:00:43"
- 1The notion of the UT second is actually quite fundamental. There are basically two different notions of time generally accepted, one based on the physical rotation of the earth (one full rotation = 1 day), the other based on the SI second (a fixed, constant value). These are radically different! Think about it, a "UT second", as defined relative to the rotation of the earth, may have a different absolute length depending on the day! Anyway, the fact that
Date
andDateTime
are based on UT seconds is a simplifying, yet honest assumption so that things like leap seconds and all their complexity can be avoided. This basis of time is formally called UT or UT1. Basing types on the UT second basically means that every minute has 60 seconds and every day has 24 hours and leads to more natural calculations when working with calendar dates.