Time

Time is an abstraction of dates and times. Time is stored internally as the number of seconds with subsecond since the Epoch, 1970-01-01 00:00:00 UTC.

The Time class treats GMT (Greenwich Mean Time) and UTC (Coordinated Universal Time) as equivalent. GMT is the older way of referring to these baseline times but persists in the names of calls on POSIX systems.

Note: A Time object uses the resolution available on your system clock.

All times may have subsecond. Be aware of this fact when comparing times with each other – times that are apparently equal when displayed may be different when compared. (Since Ruby 2.7.0, Time#inspect shows subsecond but Time#to_s still doesn’t show subsecond.)

Examples

All of these examples were done using the EST timezone which is GMT-5.

Creating a New Time Instance

You can create a new instance of Time with Time.new. This will use the current system time. Time.now is an alias for this. You can also pass parts of the time to Time.new such as year, month, minute, etc. When you want to construct a time this way you must pass at least a year. If you pass the year with nothing else time will default to January 1 of that year at 00:00:00 with the current system timezone. Here are some examples:

Time.new(2002)         #=> 2002-01-01 00:00:00 -0500
Time.new(2002, 10)     #=> 2002-10-01 00:00:00 -0500
Time.new(2002, 10, 31) #=> 2002-10-31 00:00:00 -0500

You can pass a UTC offset:

Time.new(2002, 10, 31, 2, 2, 2, "+02:00") #=> 2002-10-31 02:02:02 +0200

Or a timezone object:

zone = timezone("Europe/Athens")      # Eastern European Time, UTC+2
Time.new(2002, 10, 31, 2, 2, 2, zone) #=> 2002-10-31 02:02:02 +0200

You can also use Time.local and Time.utc to infer local and UTC timezones instead of using the current system setting.

You can also create a new time using Time.at which takes the number of seconds (with subsecond) since the Unix Epoch.

Time.at(628232400) #=> 1989-11-28 00:00:00 -0500

Working with an Instance of Time

Once you have an instance of Time there is a multitude of things you can do with it. Below are some examples. For all of the following examples, we will work on the assumption that you have done the following:

t = Time.new(1993, 02, 24, 12, 0, 0, "+09:00")

Was that a monday?

t.monday? #=> false

What year was that again?

t.year #=> 1993

Was it daylight savings at the time?

t.dst? #=> false

What’s the day a year later?

t + (60*60*24*365) #=> 1994-02-24 12:00:00 +0900

How many seconds was that since the Unix Epoch?

t.to_i #=> 730522800

You can also do standard functions like compare two times.

t1 = Time.new(2010)
t2 = Time.new(2011)

t1 == t2 #=> false
t1 == t1 #=> true
t1 <  t2 #=> true
t1 >  t2 #=> false

Time.new(2010,10,31).between?(t1, t2) #=> true

What’s Here

First, what’s elsewhere. Class Time:

• Inherits from class Object.

• Includes module Comparable.

Here, class Time provides methods that are useful for:

• Creating Time objects.

• Fetching Time values.

• Querying a Time object.

• Comparing Time objects.

• Converting a Time object.

• Rounding a Time.

Methods for Creating

• ::new: Returns a new time from specified arguments (year, month, etc.), including an optional timezone value.

• ::local (aliased as ::mktime): Same as ::new, except the timezone is the local timezone.

• ::utc (aliased as ::gm): Same as ::new, except the timezone is UTC.

• ::at: Returns a new time based on seconds since epoch.

• ::now: Returns a new time based on the current system time.

• + (plus): Returns a new time increased by the given number of seconds.

• - (minus): Returns a new time

  decreased by the given number of seconds.

Methods for Fetching

• year: Returns the year of the time.

• month (aliased as mon): Returns the month of the time.

• mday (aliased as day): Returns the day of the month.

• hour: Returns the hours value for the time.

• min: Returns the minutes value for the time.

• sec: Returns the seconds value for the time.

• usec (aliased as tv_usec): Returns the number of microseconds in the subseconds value of the time.

• nsec (aliased as tv_nsec: Returns the number of nanoseconds in the subsecond part of the time.

• subsec: Returns the subseconds value for the time.

• wday: Returns the integer weekday value of the time (0 == Sunday).

• yday: Returns the integer yearday value of the time (1 == January 1).

• hash: Returns the integer hash value for the time.

• utc_offset (aliased as gmt_offset and gmtoff): Returns the offset in seconds between time and UTC.

• to_f: Returns the float number of seconds since epoch for the time.

• to_i (aliased as tv_sec): Returns the integer number of seconds since epoch for the time.

• to_r: Returns the Rational number of seconds since epoch for the time.

• zone: Returns a string representation of the timezone of the time.

Methods for Querying

• utc? (aliased as gmt?): Returns whether the time is UTC.

• dst? (aliased as isdst): Returns whether the time is DST (daylight saving time).

• sunday?: Returns whether the time is a Sunday.

• monday?: Returns whether the time is a Monday.

• tuesday?: Returns whether the time is a Tuesday.

• wednesday?: Returns whether the time is a Wednesday.

• thursday?: Returns whether the time is a Thursday.

• friday?: Returns whether time is a Friday.

• saturday?: Returns whether the time is a Saturday.

Methods for Comparing

• #<=>: Compares self to another time.

• eql?: Returns whether the time is equal to another time.

Methods for Converting

• asctime (aliased as ctime): Returns the time as a string.

• inspect: Returns the time in detail as a string.

• strftime: Returns the time as a string, according to a given format.

• to_a: Returns a 10-element array of values from the time.

• to_s: Returns a string representation of the time.

• getutc (aliased as getgm): Returns a new time converted to UTC.

• getlocal: Returns a new time converted to local time.

• utc (aliased as gmtime): Converts time to UTC in place.

• localtime: Converts time to local time in place.

Methods for Rounding

• round:Returns a new time with subseconds rounded.

• ceil: Returns a new time with subseconds raised to a ceiling.

• floor: Returns a new time with subseconds lowered to a floor.

Timezone Argument

A timezone argument must have local_to_utc and utc_to_local methods, and may have name, abbr, and dst? methods.

The local_to_utc method should convert a Time-like object from the timezone to UTC, and utc_to_local is the opposite. The result also should be a Time or Time-like object (not necessary to be the same class). The zone of the result is just ignored. Time-like argument to these methods is similar to a Time object in UTC without subsecond; it has attribute readers for the parts, e.g. year, month, and so on, and epoch time readers, to_i. The subsecond attributes are fixed as 0, and utc_offset, zone, isdst, and their aliases are same as a Time object in UTC. Also to_time, +, and - methods are defined.

The name method is used for marshaling. If this method is not defined on a timezone object, Time objects using that timezone object can not be dumped by Marshal.

The abbr method is used by ‘%Z’ in strftime.

The dst? method is called with a Time value and should return whether the Time value is in daylight savings time in the zone.

Auto Conversion to Timezone

At loading marshaled data, a timezone name will be converted to a timezone object by find_timezone class method, if the method is defined.

Similarly, that class method will be called when a timezone argument does not have the necessary methods mentioned above.