Date & Time modules for Elixir
Status
To use timex with your projects, edit your mix.exs file and add it as a dependency:
defp deps do
[{:timex, "~> 0.6.0"}]
end
After that, run mix deps.get to load the dependency. To use Timex modules without the Timex namespace, add
use Timex to the top of each module you plan on referencing Timex from. You can then reference the modules
directly, for example: Date.now(), versus Timex.Date.now(). This is for compatibility with other libraries
which might define their own Date/DateTime/Time implementations.
Overview
This is a draft implementation of a Date/Time library for Elixir that will deal with all aspects of working with dates and time intervals.
Basically, the Date module is for dealing with dates. It supports getting current date in any time zone, converting between timezones while taking Daylight Savings Time offsets into account, calculating time intervals between two dates, shifting a date by some amount of seconds/hours/days/years towards past and future, etc. As Erlang provides support only for the Gregorian calendar, that’s what timex currently supports, but it is possible to add additional calendars if needed.
The Time module supports a finer grain level of calculations over time intervals. It is going to be used for timestamps in logs, measuring code executions times, converting time units, and so forth.
Use cases
Getting current date
Get current date in the local time zone.
date = Date.local
DateFormat.format!(date, "{ISO}") #=> "2013-09-30T16:40:08+0300"
DateFormat.format!(date, "{RFC1123}") #=> "Mon, 30 Sep 2013 16:40:08 EEST"
DateFormat.format!(date, "{kitchen}") #=> "4:40PM"
The date value that Date produced encapsulates current date, time, and time zone information. This allows for great flexibility without any overhead on the user’s part.
Since Erlang’s native date format doesn’t carry any time zone information, Date provides a bunch of constructors that take Erlang’s date value and an optional time zone.
datetime = {{2013,3,17},{21,22,23}}
date = Date.from(datetime) # datetime is assumed to be in UTC by default
DateFormat.format!(date, "{RFC1123}") #=> "Sun, 17 Mar 2013 21:22:23 GMT"
date = Date.from(datetime, :local) # indicates that datetime is in local time zone
DateFormat.format!(date, "{RFC1123}") #=> "Sun, 17 Mar 2013 21:22:23 CST"
Date.local(date) # convert date to local time zone (CST for our example)
#=> %DateTime{year: 2013, month: 3, day: 17, hour: 15, minute: 22, second: 23, timezone: ...}
# Let's see what happens if we switch the time zone
date = Date.set(date, tz: Timezone.get("EST"))
DateFormat.format!(date, "{RFC1123}")
#=> "Sun, 17 Mar 2013 17:22:23 EST"
Date.universal(date) # convert date to UTC
#=> %DateTime{year: 2013, month: 3, day: 17, hour: 21, minute: 22, second: 23, timezone: ...}Working with time zones
date = Date.from({2013,1,1}, Date.timezone("America/Chicago"))
DateFormat.format!(date, "{ISO}")
#=> "2013-01-01T00:00:00-0600"
DateFormat.format!(date, "{ISOz}")
#=> "2013-01-01T06:00:00Z"
DateFormat.format!(date, "{RFC1123}")
#=> "Tue, 01 Jan 2013 00:00:00 CST"
date = Date.now
# Convert to UTC
Date.universal(date) #=> %DateTime{...}
# Convert a date to local time
Date.local(date) #=> %DateTime{...}
# Convert a date to local time, and provide the local timezone
Date.local(date, Date.timezone("PST")) #=> %DateTime{...}Extracting information about dates
Find out current weekday, week number, number of days in a given month, etc.
date = Date.now
DateFormat.format!(date, "{RFC1123}")
#=> "Wed, 26 Feb 2014 06:02:50 GMT"
Date.weekday(date) #=> 3
Date.iso_week(date) #=> {2014, 9}
Date.iso_triplet(date) #=> {2014, 9, 3}
Date.days_in_month(date) #=> 28
Date.days_in_month(2012, 2) #=> 29
Date.is_leap?(date) #=> false
Date.is_leap?(2012) #=> true
Date.day_to_num(:mon) #=> 1
Date.day_to_num("Thursday") #=> 4 (can use Thursday, thursday, Thu, thu, :thu)
Date.day_name(4) #=> "Thursday"
Date.month_to_num(:apr) #=> 4 (same as day_to_num with possible formats)
Date.month_name(4) #=> "April"
Date arithmetic
Date can convert dates to time intervals since UNIX epoch or year 0. Calculating time intervals between two dates is possible via the diff() function (not implemented yet).
date = Date.now
DateFormat.format!(date, "{RFC1123}")
#=> "Mon, 30 Sep 2013 16:55:02 EEST"
Date.convert(date, :secs) # seconds since Epoch
#=> 1380549302
Date.to_sec(date, :zero) # seconds since year 0
#=> 63547768502
DateFormat.format!(Date.epoch(), "{ISO}")
#=> "1970-01-01T00:00:00+0000"
Date.epoch(:secs) # seconds since year 0 to Epoch
#=> 62167219200
date = Date.from(Date.epoch(:secs) + 144, :secs, :zero) # :zero indicates year 0
DateFormat.format!(date, "{ISOz}")
#=> "1970-01-01T00:02:24Z"Shifting dates
Shifting refers to moving by some amount of time towards past or future. Date supports multiple ways of doing this.
date = Date.now
DateFormat.format!(date, "{RFC1123}")
#=> "Mon, 30 Sep 2013 16:58:13 EEST"
DateFormat.format!( Date.shift(date, secs: 78), "{RFC1123}" )
#=> "Mon, 30 Sep 2013 16:59:31 EEST"
DateFormat.format!( Date.shift(date, secs: -1078), "{RFC1123}" )
#=> "Mon, 30 Sep 2013 16:40:15 EEST"
DateFormat.format!( Date.shift(date, days: 1), "{RFC1123}" )
#=> "Tue, 01 Oct 2013 16:58:13 EEST"
DateFormat.format!( Date.shift(date, weeks: 3), "{RFC1123}" )
#=> "Mon, 21 Oct 2013 16:58:13 EEST"
DateFormat.format!( Date.shift(date, years: -13), "{RFC1123}" )
#=> "Sat, 30 Sep 2000 16:58:13 EEST"Working with Time module
The Time module already has some conversions and functionality for measuring time.
## Time.now returns time since UNIX epoch ##
Time.now
#=> {1362,781057,813380}
Time.now(:secs)
#=> 1362781082.040016
Time.now(:msecs)
#=> 1362781088623.741
## Converting units is easy ##
t = Time.now
#=> {1362,781097,857429}
Time.to_usecs(t)
#=> 1362781097857429.0
Time.to_secs(t)
#=> 1362781097.857429
Time.to_secs(13, :hours)
#=> 46800
Time.to_secs(13, :msecs)
#=> 0.013
## We can also convert from timestamps to other units using a single function ##
Time.convert(t, :secs)
#=> 1362781097.857429
Time.convert(t, :mins)
#=> 22713018.297623817
Time.convert(t, :hours)
#=> 378550.30496039696
## elapsed() calculates time interval between now and t ##
Time.elapsed(t)
#=> {0,68,-51450}
Time.elapsed(t, :secs)
#=> 72.100247
t1 = Time.elapsed(t)
#=> {0,90,-339935}
## diff() calculates time interval between two timestamps ##
Time.diff(t1, t)
#=> {-1362,-781007,-1197364}
Time.diff(Time.now, t)
#=> {0,105,-300112}
Time.diff(Time.now, t, :hours)
#=> 0.03031450388888889Converting time units
dt = Time.now
Time.convert(dt, :secs)
Time.convert(dt, :mins)
Time.convert(dt, :hours)
Time.to_timestamp(13, :secs)FAQ
Which functions provide microsecond precision?
If you need to work with time intervals down to microsecond precision, you should take a look at the functions in the Time module. The Date module is designed for things like handling different time zones and working with dates separated by large intervals, so the minimum time unit it uses is seconds.
So how do I work with time intervals defined with microsecond precision?
Use functions from the Time module for time interval arithmetic.
How do I find the time interval between two dates?
Use Date.diff to obtain the number of seconds, minutes, hours, days, months, weeks, or years between two dates.
What kind of operations is this lib going to support eventually?
The goal is to make it so you never have to use Erlang’s calendar/time functions.
Some inspirations I’m currently drawing from:
- Moment.js
- JodaTime
What is the support for time zones?
Full support for retreiving local timezone configuration on OSX, *NIX, and Windows, conversion to any timezone in the Olson timezone database, and full support for daylight savings time transitions.
Timezone support is also exposed via the Timezone, Timezone.Local, and Timezone.Dst modules. Their functionality is exposed via the Date module’s API, and most common use cases shouldn’t need to access the Timezone namespace directly, but it’s there if needed.
License
This software is licensed under the MIT license.