Creates a new Time object with the value given by time, the given number of seconds_with_frac, or seconds and microseconds_with_frac since the Epoch. seconds_with_frac and microseconds_with_frac can be an Integer, Float, Rational, or other Numeric. non-portable feature allows the offset to be negative on some systems.

If in argument is given, the result is in that timezone or UTC offset, or if a numeric argument is given, the result is in local time.

Time.at(0)                                #=> 1969-12-31 18:00:00 -0600
Time.at(Time.at(0))                       #=> 1969-12-31 18:00:00 -0600
Time.at(946702800)                        #=> 1999-12-31 23:00:00 -0600
Time.at(-284061600)                       #=> 1960-12-31 00:00:00 -0600
Time.at(946684800.2).usec                 #=> 200000
Time.at(946684800, 123456.789).nsec       #=> 123456789
Time.at(946684800, 123456789, :nsec).nsec #=> 123456789

Creates a Time object based on given values, interpreted as UTC (GMT). The year must be specified. Other values default to the minimum value for that field (and may be nil or omitted). Months may be specified by numbers from 1 to 12, or by the three-letter English month names. Hours are specified on a 24-hour clock (0..23). Raises an ArgumentError if any values are out of range. Will also accept ten arguments in the order output by Time#to_a.

sec_with_frac and usec_with_frac can have a fractional part.

Time.utc(2000,"jan",1,20,15,1)  #=> 2000-01-01 20:15:01 UTC
Time.gm(2000,"jan",1,20,15,1)   #=> 2000-01-01 20:15:01 UTC

Parses date as an HTTP-date defined by RFC 2616 and converts it to a Time object.

ArgumentError is raised if date is not compliant with RFC 2616 or if the Time class cannot represent specified date.

See httpdate for more information on this format.

require 'time'

Time.httpdate("Thu, 06 Oct 2011 02:26:12 GMT")
#=> 2011-10-06 02:26:12 UTC

You must require ‘time’ to use this method.

Deserializes JSON string by converting time since epoch to Time

Same as Time::gm, but interprets the values in the local time zone.

Time.local(2000,"jan",1,20,15,1)   #=> 2000-01-01 20:15:01 -0600

Same as Time::gm, but interprets the values in the local time zone.

Time.local(2000,"jan",1,20,15,1)   #=> 2000-01-01 20:15:01 -0600

Returns a Time object.

It is initialized to the current system time if no argument is given.

Note: The new object will use the resolution available on your system clock, and may include fractional seconds.

If one or more arguments are specified, the time is initialized to the specified time.

sec may have fraction if it is a rational.

tz specifies the timezone. It can be an offset from UTC, given either as a string such as “+09:00” or as a number of seconds such as 32400. Or it can be a timezone object, see Timezone argument for details.

a = Time.new      #=> 2007-11-19 07:50:02 -0600
b = Time.new      #=> 2007-11-19 07:50:02 -0600
a == b            #=> false
"%.6f" % a.to_f   #=> "1195480202.282373"
"%.6f" % b.to_f   #=> "1195480202.283415"

Time.new(2008,6,21, 13,30,0, "+09:00") #=> 2008-06-21 13:30:00 +0900

# A trip for RubyConf 2007
t1 = Time.new(2007,11,1,15,25,0, "+09:00") # JST (Narita)
t2 = Time.new(2007,11,1,12, 5,0, "-05:00") # CDT (Minneapolis)
t3 = Time.new(2007,11,1,13,25,0, "-05:00") # CDT (Minneapolis)
t4 = Time.new(2007,11,1,16,53,0, "-04:00") # EDT (Charlotte)
t5 = Time.new(2007,11,5, 9,24,0, "-05:00") # EST (Charlotte)
t6 = Time.new(2007,11,5,11,21,0, "-05:00") # EST (Detroit)
t7 = Time.new(2007,11,5,13,45,0, "-05:00") # EST (Detroit)
t8 = Time.new(2007,11,6,17,10,0, "+09:00") # JST (Narita)
(t2-t1)/3600.0                             #=> 10.666666666666666
(t4-t3)/3600.0                             #=> 2.466666666666667
(t6-t5)/3600.0                             #=> 1.95
(t8-t7)/3600.0                             #=> 13.416666666666666

Creates a new Time object for the current time. This is same as Time.new without arguments.

Time.now            #=> 2009-06-24 12:39:54 +0900

Takes a string representation of a Time and attempts to parse it using a heuristic.

require 'time'

Time.parse("2010-10-31") #=> 2010-10-31 00:00:00 -0500

Any missing pieces of the date are inferred based on the current date.

require 'time'

# assuming the current date is "2011-10-31"
Time.parse("12:00") #=> 2011-10-31 12:00:00 -0500

We can change the date used to infer our missing elements by passing a second object that responds to mon, day and year, such as Date, Time or DateTime. We can also use our own object.

require 'time'

class MyDate
  attr_reader :mon, :day, :year

  def initialize(mon, day, year)
    @mon, @day, @year = mon, day, year
  end
end

d  = Date.parse("2010-10-28")
t  = Time.parse("2010-10-29")
dt = DateTime.parse("2010-10-30")
md = MyDate.new(10,31,2010)

Time.parse("12:00", d)  #=> 2010-10-28 12:00:00 -0500
Time.parse("12:00", t)  #=> 2010-10-29 12:00:00 -0500
Time.parse("12:00", dt) #=> 2010-10-30 12:00:00 -0500
Time.parse("12:00", md) #=> 2010-10-31 12:00:00 -0500

If a block is given, the year described in date is converted by the block. This is specifically designed for handling two digit years. For example, if you wanted to treat all two digit years prior to 70 as the year 2000+ you could write this:

require 'time'

Time.parse("01-10-31") {|year| year + (year < 70 ? 2000 : 1900)}
#=> 2001-10-31 00:00:00 -0500
Time.parse("70-10-31") {|year| year + (year < 70 ? 2000 : 1900)}
#=> 1970-10-31 00:00:00 -0500

If the upper components of the given time are broken or missing, they are supplied with those of now. For the lower components, the minimum values (1 or 0) are assumed if broken or missing. For example:

require 'time'

# Suppose it is "Thu Nov 29 14:33:20 2001" now and
# your time zone is EST which is GMT-5.
now = Time.parse("Thu Nov 29 14:33:20 2001")
Time.parse("16:30", now)     #=> 2001-11-29 16:30:00 -0500
Time.parse("7/23", now)      #=> 2001-07-23 00:00:00 -0500
Time.parse("Aug 31", now)    #=> 2001-08-31 00:00:00 -0500
Time.parse("Aug 2000", now)  #=> 2000-08-01 00:00:00 -0500

Since there are numerous conflicts among locally defined time zone abbreviations all over the world, this method is not intended to understand all of them. For example, the abbreviation “CST” is used variously as:

-06:00 in America/Chicago,
-05:00 in America/Havana,
+08:00 in Asia/Harbin,
+09:30 in Australia/Darwin,
+10:30 in Australia/Adelaide,
etc.

Based on this fact, this method only understands the time zone abbreviations described in RFC 822 and the system time zone, in the order named. (i.e. a definition in RFC 822 overrides the system time zone definition.) The system time zone is taken from Time.local(year, 1, 1).zone and Time.local(year, 7, 1).zone. If the extracted time zone abbreviation does not match any of them, it is ignored and the given time is regarded as a local time.

ArgumentError is raised if Date._parse cannot extract information from date or if the Time class cannot represent specified date.

This method can be used as a fail-safe for other parsing methods as:

Time.rfc2822(date) rescue Time.parse(date)
Time.httpdate(date) rescue Time.parse(date)
Time.xmlschema(date) rescue Time.parse(date)

A failure of Time.parse should be checked, though.

You must require ‘time’ to use this method.

Parses date as date-time defined by RFC 2822 and converts it to a Time object. The format is identical to the date format defined by RFC 822 and updated by RFC 1123.

ArgumentError is raised if date is not compliant with RFC 2822 or if the Time class cannot represent specified date.

See rfc2822 for more information on this format.

require 'time'

Time.rfc2822("Wed, 05 Oct 2011 22:26:12 -0400")
#=> 2010-10-05 22:26:12 -0400

You must require ‘time’ to use this method.

Works similar to parse except that instead of using a heuristic to detect the format of the input string, you provide a second argument that describes the format of the string.

If a block is given, the year described in date is converted by the block. For example:

Time.strptime(...) {|y| y < 100 ? (y >= 69 ? y + 1900 : y + 2000) : y}

Below is a list of the formatting options:

%a

The abbreviated weekday name (“Sun”)

%A

The full weekday name (“Sunday”)

%b

The abbreviated month name (“Jan”)

%B

The full month name (“January”)

%c

The preferred local date and time representation

%C

Century (20 in 2009)

%d

Day of the month (01..31)

%D

Date (%m/%d/%y)

%e

Day of the month, blank-padded ( 1..31)

%F

Equivalent to %Y-%m-%d (the ISO 8601 date format)

%h

Equivalent to %b

%H

Hour of the day, 24-hour clock (00..23)

%I

Hour of the day, 12-hour clock (01..12)

%j

Day of the year (001..366)

%k

hour, 24-hour clock, blank-padded ( 0..23)

%l

hour, 12-hour clock, blank-padded ( 0..12)

%L

Millisecond of the second (000..999)

%m

Month of the year (01..12)

%M

Minute of the hour (00..59)

%n

Newline (n)

%N

Fractional seconds digits

%p

Meridian indicator (“AM” or “PM”)

%P

Meridian indicator (“am” or “pm”)

%Q

Number of milliseconds since 1970-01-01 00:00:00 UTC.

%r

time, 12-hour (same as %I:%M:%S %p)

%R

time, 24-hour (%H:%M)

%s

Number of seconds since 1970-01-01 00:00:00 UTC.

%S

Second of the minute (00..60)

%t

Tab character (t)

%T

time, 24-hour (%H:%M:%S)

%u

Day of the week as a decimal, Monday being 1. (1..7)

%U

Week number of the current year, starting with the first Sunday as the first day of the first week (00..53)

%v

VMS date (%e-%b-%Y)

%V

Week number of year according to ISO 8601 (01..53)

%W

Week number of the current year, starting with the first Monday as the first day of the first week (00..53)

%w

Day of the week (Sunday is 0, 0..6)

%x

Preferred representation for the date alone, no time

%X

Preferred representation for the time alone, no date

%y

Year without a century (00..99)

%Y

Year which may include century, if provided

%z

Time zone as hour offset from UTC (e.g. +0900)

%Z

Time zone name

%%

Literal “%” character

%+

date(1) (%a %b %e %H:%M:%S %Z %Y)

require 'time'

Time.strptime("2000-10-31", "%Y-%m-%d") #=> 2000-10-31 00:00:00 -0500

You must require ‘time’ to use this method.

Creates a Time object based on given values, interpreted as UTC (GMT). The year must be specified. Other values default to the minimum value for that field (and may be nil or omitted). Months may be specified by numbers from 1 to 12, or by the three-letter English month names. Hours are specified on a 24-hour clock (0..23). Raises an ArgumentError if any values are out of range. Will also accept ten arguments in the order output by Time#to_a.

sec_with_frac and usec_with_frac can have a fractional part.

Time.utc(2000,"jan",1,20,15,1)  #=> 2000-01-01 20:15:01 UTC
Time.gm(2000,"jan",1,20,15,1)   #=> 2000-01-01 20:15:01 UTC

This method converts a W3CDTF string date/time format to Time object.

The W3CDTF format is defined here: www.w3.org/TR/NOTE-datetime

Time.w3cdtf('2003-02-15T13:50:05-05:00')
# => 2003-02-15 10:50:05 -0800
Time.w3cdtf('2003-02-15T13:50:05-05:00').class
# => Time

Parses date as a dateTime defined by the XML Schema and converts it to a Time object. The format is a restricted version of the format defined by ISO 8601.

ArgumentError is raised if date is not compliant with the format or if the Time class cannot represent specified date.

See xmlschema for more information on this format.

require 'time'

Time.xmlschema("2011-10-05T22:26:12-04:00")
#=> 2011-10-05 22:26:12-04:00

You must require ‘time’ to use this method.

Return the number of seconds the specified time zone differs from UTC.

Numeric time zones that include minutes, such as -10:00 or +1330 will work, as will simpler hour-only time zones like -10 or +13.

Textual time zones listed in ZoneOffset are also supported.

If the time zone does not match any of the above, zone_offset will check if the local time zone (both with and without potential Daylight Saving Time changes being in effect) matches zone. Specifying a value for year will change the year used to find the local time zone.

If zone_offset is unable to determine the offset, nil will be returned.

require 'time'

Time.zone_offset("EST") #=> -18000

You must require ‘time’ to use this method.

Addition — Adds some number of seconds (possibly fractional) to time and returns that value as a new Time object.

t = Time.now         #=> 2007-11-19 08:22:21 -0600
t + (60 * 60 * 24)   #=> 2007-11-20 08:22:21 -0600

Difference — Returns a difference in seconds as a Float between time and other_time, or subtracts the given number of seconds in numeric from time.

t = Time.now       #=> 2007-11-19 08:23:10 -0600
t2 = t + 2592000   #=> 2007-12-19 08:23:10 -0600
t2 - t             #=> 2592000.0
t2 - 2592000       #=> 2007-11-19 08:23:10 -0600

Comparison—Compares time with other_time.

-1, 0, +1 or nil depending on whether time is less than, equal to, or greater than other_time.

nil is returned if the two values are incomparable.

t = Time.now       #=> 2007-11-19 08:12:12 -0600
t2 = t + 2592000   #=> 2007-12-19 08:12:12 -0600
t <=> t2           #=> -1
t2 <=> t           #=> 1

t = Time.now       #=> 2007-11-19 08:13:38 -0600
t2 = t + 0.1       #=> 2007-11-19 08:13:38 -0600
t.nsec             #=> 98222999
t2.nsec            #=> 198222999
t <=> t2           #=> -1
t2 <=> t           #=> 1
t <=> t            #=> 0

Returns a hash, that will be turned into a JSON object and represent this object.

Returns a canonical string representation of time.

Time.now.asctime   #=> "Wed Apr  9 08:56:03 2003"
Time.now.ctime     #=> "Wed Apr  9 08:56:03 2003"

Returns true if time and other_time are both Time objects with the same seconds and fractional seconds.

Returns true if time represents Friday.

t = Time.local(1987, 12, 18)     #=> 1987-12-18 00:00:00 -0600
t.friday?                        #=> true

Returns a new Time object representing time in UTC.

t = Time.local(2000,1,1,20,15,1)   #=> 2000-01-01 20:15:01 -0600
t.gmt?                             #=> false
y = t.getgm                        #=> 2000-01-02 02:15:01 UTC
y.gmt?                             #=> true
t == y                             #=> true

Returns a new Time object representing time in local time (using the local time zone in effect for this process).

If utc_offset is given, it is used instead of the local time. utc_offset can be given as a human-readable string (eg. "+09:00") or as a number of seconds (eg. 32400).

t = Time.utc(2000,1,1,20,15,1)  #=> 2000-01-01 20:15:01 UTC
t.utc?                          #=> true

l = t.getlocal                  #=> 2000-01-01 14:15:01 -0600
l.utc?                          #=> false
t == l                          #=> true

j = t.getlocal("+09:00")        #=> 2000-01-02 05:15:01 +0900
j.utc?                          #=> false
t == j                          #=> true

k = t.getlocal(9*60*60)         #=> 2000-01-02 05:15:01 +0900
k.utc?                          #=> false
t == k                          #=> true

Converts time to UTC (GMT), modifying the receiver.

t = Time.now   #=> 2007-11-19 08:18:31 -0600
t.gmt?         #=> false
t.gmtime       #=> 2007-11-19 14:18:31 UTC
t.gmt?         #=> true

t = Time.now   #=> 2007-11-19 08:18:51 -0600
t.utc?         #=> false
t.utc          #=> 2007-11-19 14:18:51 UTC
t.utc?         #=> true

Returns the offset in seconds between the timezone of time and UTC.

t = Time.gm(2000,1,1,20,15,1)   #=> 2000-01-01 20:15:01 UTC
t.gmt_offset                    #=> 0
l = t.getlocal                  #=> 2000-01-01 14:15:01 -0600
l.gmt_offset                    #=> -21600

Returns a hash code for this Time object.

See also Object#hash.

Returns the hour of the day (0..23) for time.

t = Time.now   #=> 2007-11-19 08:26:20 -0600
t.hour         #=> 8

Returns a string which represents the time as RFC 1123 date of HTTP-date defined by RFC 2616:

day-of-week, DD month-name CCYY hh:mm:ss GMT

Note that the result is always UTC (GMT).

require 'time'

t = Time.now
t.httpdate # => "Thu, 06 Oct 2011 02:26:12 GMT"

You must require ‘time’ to use this method.

Returns true if time occurs during Daylight Saving Time in its time zone.

# CST6CDT:
  Time.local(2000, 1, 1).zone    #=> "CST"
  Time.local(2000, 1, 1).isdst   #=> false
  Time.local(2000, 1, 1).dst?    #=> false
  Time.local(2000, 7, 1).zone    #=> "CDT"
  Time.local(2000, 7, 1).isdst   #=> true
  Time.local(2000, 7, 1).dst?    #=> true

# Asia/Tokyo:
  Time.local(2000, 1, 1).zone    #=> "JST"
  Time.local(2000, 1, 1).isdst   #=> false
  Time.local(2000, 1, 1).dst?    #=> false
  Time.local(2000, 7, 1).zone    #=> "JST"
  Time.local(2000, 7, 1).isdst   #=> false
  Time.local(2000, 7, 1).dst?    #=> false

Converts time to local time (using the local time zone in effect at the creation time of time) modifying the receiver.

If utc_offset is given, it is used instead of the local time.

t = Time.utc(2000, "jan", 1, 20, 15, 1) #=> 2000-01-01 20:15:01 UTC
t.utc?                                  #=> true

t.localtime                             #=> 2000-01-01 14:15:01 -0600
t.utc?                                  #=> false

t.localtime("+09:00")                   #=> 2000-01-02 05:15:01 +0900
t.utc?                                  #=> false

If utc_offset is not given and time is local time, just returns the receiver.

Returns the day of the month (1..n) for time.

t = Time.now   #=> 2007-11-19 08:27:03 -0600
t.day          #=> 19
t.mday         #=> 19

Returns the minute of the hour (0..59) for time.

t = Time.now   #=> 2007-11-19 08:25:51 -0600
t.min          #=> 25

Returns the month of the year (1..12) for time.

t = Time.now   #=> 2007-11-19 08:27:30 -0600
t.mon          #=> 11
t.month        #=> 11

Returns true if time represents Monday.

t = Time.local(2003, 8, 4)       #=> 2003-08-04 00:00:00 -0500
t.monday?                        #=> true

Returns a string which represents the time as date-time defined by RFC 2822:

day-of-week, DD month-name CCYY hh:mm:ss zone

where zone is [+-]hhmm.

If self is a UTC time, -0000 is used as zone.

require 'time'

t = Time.now
t.rfc2822  # => "Wed, 05 Oct 2011 22:26:12 -0400"

You must require ‘time’ to use this method.

Rounds sub seconds to a given precision in decimal digits (0 digits by default). It returns a new Time object. ndigits should be zero or a positive integer.

require 'time'

t = Time.utc(2010,3,30, 5,43,"25.123456789".to_r)
t.iso8601(10)           #=> "2010-03-30T05:43:25.1234567890Z"
t.round.iso8601(10)     #=> "2010-03-30T05:43:25.0000000000Z"
t.round(0).iso8601(10)  #=> "2010-03-30T05:43:25.0000000000Z"
t.round(1).iso8601(10)  #=> "2010-03-30T05:43:25.1000000000Z"
t.round(2).iso8601(10)  #=> "2010-03-30T05:43:25.1200000000Z"
t.round(3).iso8601(10)  #=> "2010-03-30T05:43:25.1230000000Z"
t.round(4).iso8601(10)  #=> "2010-03-30T05:43:25.1235000000Z"
t.round(5).iso8601(10)  #=> "2010-03-30T05:43:25.1234600000Z"
t.round(6).iso8601(10)  #=> "2010-03-30T05:43:25.1234570000Z"
t.round(7).iso8601(10)  #=> "2010-03-30T05:43:25.1234568000Z"
t.round(8).iso8601(10)  #=> "2010-03-30T05:43:25.1234567900Z"
t.round(9).iso8601(10)  #=> "2010-03-30T05:43:25.1234567890Z"
t.round(10).iso8601(10) #=> "2010-03-30T05:43:25.1234567890Z"

t = Time.utc(1999,12,31, 23,59,59)
(t + 0.4).round.iso8601(3)    #=> "1999-12-31T23:59:59.000Z"
(t + 0.49).round.iso8601(3)   #=> "1999-12-31T23:59:59.000Z"
(t + 0.5).round.iso8601(3)    #=> "2000-01-01T00:00:00.000Z"
(t + 1.4).round.iso8601(3)    #=> "2000-01-01T00:00:00.000Z"
(t + 1.49).round.iso8601(3)   #=> "2000-01-01T00:00:00.000Z"
(t + 1.5).round.iso8601(3)    #=> "2000-01-01T00:00:01.000Z"

t = Time.utc(1999,12,31, 23,59,59)
(t + 0.123456789).round(4).iso8601(6)  #=> "1999-12-31T23:59:59.123500Z"

Returns true if time represents Saturday.

t = Time.local(2006, 6, 10)      #=> 2006-06-10 00:00:00 -0500
t.saturday?                      #=> true

Returns the second of the minute (0..60) for time.

Note: Seconds range from zero to 60 to allow the system to inject leap seconds. See en.wikipedia.org/wiki/Leap_second for further details.

t = Time.now   #=> 2007-11-19 08:25:02 -0600
t.sec          #=> 2

Formats time according to the directives in the given format string.

The directives begin with a percent (%) character. Any text not listed as a directive will be passed through to the output string.

The directive consists of a percent (%) character, zero or more flags, optional minimum field width, optional modifier and a conversion specifier as follows:

%<flags><width><modifier><conversion>

Flags:

-  don't pad a numerical output
_  use spaces for padding
0  use zeros for padding
^  upcase the result string
#  change case
:  use colons for %z

The minimum field width specifies the minimum width.

The modifiers are “E” and “O”. They are ignored.

Format directives:

Date (Year, Month, Day):
  %Y - Year with century if provided, will pad result at least 4 digits.
          -0001, 0000, 1995, 2009, 14292, etc.
  %C - year / 100 (rounded down such as 20 in 2009)
  %y - year % 100 (00..99)

  %m - Month of the year, zero-padded (01..12)
          %_m  blank-padded ( 1..12)
          %-m  no-padded (1..12)
  %B - The full month name (``January'')
          %^B  uppercased (``JANUARY'')
  %b - The abbreviated month name (``Jan'')
          %^b  uppercased (``JAN'')
  %h - Equivalent to %b

  %d - Day of the month, zero-padded (01..31)
          %-d  no-padded (1..31)
  %e - Day of the month, blank-padded ( 1..31)

  %j - Day of the year (001..366)

Time (Hour, Minute, Second, Subsecond):
  %H - Hour of the day, 24-hour clock, zero-padded (00..23)
  %k - Hour of the day, 24-hour clock, blank-padded ( 0..23)
  %I - Hour of the day, 12-hour clock, zero-padded (01..12)
  %l - Hour of the day, 12-hour clock, blank-padded ( 1..12)
  %P - Meridian indicator, lowercase (``am'' or ``pm'')
  %p - Meridian indicator, uppercase (``AM'' or ``PM'')

  %M - Minute of the hour (00..59)

  %S - Second of the minute (00..60)

  %L - Millisecond of the second (000..999)
       The digits under millisecond are truncated to not produce 1000.
  %N - Fractional seconds digits, default is 9 digits (nanosecond)
          %3N  millisecond (3 digits)
          %6N  microsecond (6 digits)
          %9N  nanosecond (9 digits)
          %12N picosecond (12 digits)
          %15N femtosecond (15 digits)
          %18N attosecond (18 digits)
          %21N zeptosecond (21 digits)
          %24N yoctosecond (24 digits)
       The digits under the specified length are truncated to avoid
       carry up.

Time zone:
  %z - Time zone as hour and minute offset from UTC (e.g. +0900)
          %:z - hour and minute offset from UTC with a colon (e.g. +09:00)
          %::z - hour, minute and second offset from UTC (e.g. +09:00:00)
  %Z - Abbreviated time zone name or similar information.  (OS dependent)

Weekday:
  %A - The full weekday name (``Sunday'')
          %^A  uppercased (``SUNDAY'')
  %a - The abbreviated name (``Sun'')
          %^a  uppercased (``SUN'')
  %u - Day of the week (Monday is 1, 1..7)
  %w - Day of the week (Sunday is 0, 0..6)

ISO 8601 week-based year and week number:
The first week of YYYY starts with a Monday and includes YYYY-01-04.
The days in the year before the first week are in the last week of
the previous year.
  %G - The week-based year
  %g - The last 2 digits of the week-based year (00..99)
  %V - Week number of the week-based year (01..53)

Week number:
The first week of YYYY that starts with a Sunday or Monday (according to %U
or %W). The days in the year before the first week are in week 0.
  %U - Week number of the year. The week starts with Sunday. (00..53)
  %W - Week number of the year. The week starts with Monday. (00..53)

Seconds since the Epoch:
  %s - Number of seconds since 1970-01-01 00:00:00 UTC.

Literal string:
  %n - Newline character (\n)
  %t - Tab character (\t)
  %% - Literal ``%'' character

Combination:
  %c - date and time (%a %b %e %T %Y)
  %D - Date (%m/%d/%y)
  %F - The ISO 8601 date format (%Y-%m-%d)
  %v - VMS date (%e-%^b-%4Y)
  %x - Same as %D
  %X - Same as %T
  %r - 12-hour time (%I:%M:%S %p)
  %R - 24-hour time (%H:%M)
  %T - 24-hour time (%H:%M:%S)

This method is similar to strftime() function defined in ISO C and POSIX.

While all directives are locale independent since Ruby 1.9, %Z is platform dependent. So, the result may differ even if the same format string is used in other systems such as C.

%z is recommended over %Z. %Z doesn’t identify the timezone. For example, “CST” is used at America/Chicago (-06:00), America/Havana (-05:00), Asia/Harbin (+08:00), Australia/Darwin (+09:30) and Australia/Adelaide (+10:30). Also, %Z is highly dependent on the operating system. For example, it may generate a non ASCII string on Japanese Windows, i.e. the result can be different to “JST”. So the numeric time zone offset, %z, is recommended.

Examples:

t = Time.new(2007,11,19,8,37,48,"-06:00") #=> 2007-11-19 08:37:48 -0600
t.strftime("Printed on %m/%d/%Y")         #=> "Printed on 11/19/2007"
t.strftime("at %I:%M %p")                 #=> "at 08:37 AM"

Various ISO 8601 formats:

%Y%m%d           => 20071119                  Calendar date (basic)
%F               => 2007-11-19                Calendar date (extended)
%Y-%m            => 2007-11                   Calendar date, reduced accuracy, specific month
%Y               => 2007                      Calendar date, reduced accuracy, specific year
%C               => 20                        Calendar date, reduced accuracy, specific century
%Y%j             => 2007323                   Ordinal date (basic)
%Y-%j            => 2007-323                  Ordinal date (extended)
%GW%V%u          => 2007W471                  Week date (basic)
%G-W%V-%u        => 2007-W47-1                Week date (extended)
%GW%V            => 2007W47                   Week date, reduced accuracy, specific week (basic)
%G-W%V           => 2007-W47                  Week date, reduced accuracy, specific week (extended)
%H%M%S           => 083748                    Local time (basic)
%T               => 08:37:48                  Local time (extended)
%H%M             => 0837                      Local time, reduced accuracy, specific minute (basic)
%H:%M            => 08:37                     Local time, reduced accuracy, specific minute (extended)
%H               => 08                        Local time, reduced accuracy, specific hour
%H%M%S,%L        => 083748,000                Local time with decimal fraction, comma as decimal sign (basic)
%T,%L            => 08:37:48,000              Local time with decimal fraction, comma as decimal sign (extended)
%H%M%S.%L        => 083748.000                Local time with decimal fraction, full stop as decimal sign (basic)
%T.%L            => 08:37:48.000              Local time with decimal fraction, full stop as decimal sign (extended)
%H%M%S%z         => 083748-0600               Local time and the difference from UTC (basic)
%T%:z            => 08:37:48-06:00            Local time and the difference from UTC (extended)
%Y%m%dT%H%M%S%z  => 20071119T083748-0600      Date and time of day for calendar date (basic)
%FT%T%:z         => 2007-11-19T08:37:48-06:00 Date and time of day for calendar date (extended)
%Y%jT%H%M%S%z    => 2007323T083748-0600       Date and time of day for ordinal date (basic)
%Y-%jT%T%:z      => 2007-323T08:37:48-06:00   Date and time of day for ordinal date (extended)
%GW%V%uT%H%M%S%z => 2007W471T083748-0600      Date and time of day for week date (basic)
%G-W%V-%uT%T%:z  => 2007-W47-1T08:37:48-06:00 Date and time of day for week date (extended)
%Y%m%dT%H%M      => 20071119T0837             Calendar date and local time (basic)
%FT%R            => 2007-11-19T08:37          Calendar date and local time (extended)
%Y%jT%H%MZ       => 2007323T0837Z             Ordinal date and UTC of day (basic)
%Y-%jT%RZ        => 2007-323T08:37Z           Ordinal date and UTC of day (extended)
%GW%V%uT%H%M%z   => 2007W471T0837-0600        Week date and local time and difference from UTC (basic)
%G-W%V-%uT%R%:z  => 2007-W47-1T08:37-06:00    Week date and local time and difference from UTC (extended)

Returns the fraction for time.

The return value can be a rational number.

t = Time.now        #=> 2009-03-26 22:33:12 +0900
"%10.9f" % t.to_f   #=> "1238074392.940563917"
t.subsec            #=> (94056401/100000000)

The lowest digits of to_f and subsec are different because IEEE 754 double is not accurate enough to represent the rational number.

The more accurate value is returned by subsec.