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Class: DateTime

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::Date
Instance Chain:
self, ::Date, Comparable
Inherits: Date
Defined in: ext/date/date_core.c

Overview

A subclass of ::Date that easily handles date, hour, minute, second, and offset.

DateTime does not consider any leap seconds, does not track any summer time rules.

A DateTime object is created with .new, .jd, .ordinal, .commercial, .parse, .strptime, .now, Time#to_datetime, etc.

require 'date'

DateTime.new(2001,2,3,4,5,6)
                    #=> #<DateTime: 2001-02-03T04:05:06+00:00 ...>

The last element of day, hour, minute, or second can be a fractional number. The fractional number's precision is assumed at most nanosecond.

DateTime.new(2001,2,3.5)
                    #=> #<DateTime: 2001-02-03T12:00:00+00:00 ...>

An optional argument, the offset, indicates the difference between the local time and UTC. For example, Rational(3,24) represents ahead of 3 hours of UTC, Rational(-5,24) represents behind of 5 hours of UTC. The offset should be -1 to +1, and its precision is assumed at most second. The default value is zero (equals to UTC).

DateTime.new(2001,2,3,4,5,6,Rational(3,24))
                    #=> #<DateTime: 2001-02-03T04:05:06+03:00 ...>

The offset also accepts string form:

DateTime.new(2001,2,3,4,5,6,'+03:00')
                    #=> #<DateTime: 2001-02-03T04:05:06+03:00 ...>

An optional argument, the day of calendar reform (start), denotes a Julian day number, which should be 2298874 to 2426355 or negative/positive infinity. The default value is Date::ITALY (2299161=1582-10-15).

A DateTime object has various methods. See each reference.

d = DateTime.parse('3rd Feb 2001 04:05:06+03:30')
                    #=> #<DateTime: 2001-02-03T04:05:06+03:30 ...>
d.hour              #=> 4
d.min               #=> 5
d.sec               #=> 6
d.offset            #=> (7/48)
d.zone              #=> "+03:30"
d += Rational('1.5')
                    #=> #<DateTime: 2001-02-04%16:05:06+03:30 ...>
d = d.new_offset('+09:00')
                    #=> #<DateTime: 2001-02-04%21:35:06+09:00 ...>
d.strftime('%I:%M:%S %p')
                    #=> "09:35:06 PM"
d > DateTime.new(1999)
                    #=> true

When should you use DateTime and when should you use Time?

It's a common misconception that William Shakespeare and Miguel de Cervantes died on the same day in history - so much so that UNESCO named April 23 as World Book Day because of this fact. However, because England hadn't yet adopted the Gregorian Calendar Reform (and wouldn't until 1752) their deaths are actually 10 days apart. Since Ruby's ::Time class implements a proleptic Gregorian calendar and has no concept of calendar reform there's no way to express this with ::Time objects. This is where DateTime steps in:

shakespeare = DateTime.iso8601('1616-04-23', Date::ENGLAND)
 #=> Tue, 23 Apr 1616 00:00:00 +0000
cervantes = DateTime.iso8601('1616-04-23', Date::ITALY)
 #=> Sat, 23 Apr 1616 00:00:00 +0000

Already you can see something is weird - the days of the week are different. Taking this further:

cervantes == shakespeare
 #=> false
(shakespeare - cervantes).to_i
 #=> 10

This shows that in fact they died 10 days apart (in reality 11 days since Cervantes died a day earlier but was buried on the 23rd). We can see the actual date of Shakespeare's death by using the #gregorian method to convert it:

shakespeare.gregorian
 #=> Tue, 03 May 1616 00:00:00 +0000

So there's an argument that all the celebrations that take place on the 23rd April in Stratford-upon-Avon are actually the wrong date since England is now using the Gregorian calendar. You can see why when we transition across the reform date boundary:

# start off with the anniversary of Shakespeare's birth in 1751
shakespeare = DateTime.iso8601('1751-04-23', Date::ENGLAND)
 #=> Tue, 23 Apr 1751 00:00:00 +0000

# add 366 days since 1752 is a leap year and April 23 is after February 29
shakespeare + 366
 #=> Thu, 23 Apr 1752 00:00:00 +0000

# add another 365 days to take us to the anniversary in 1753
shakespeare + 366 + 365
 #=> Fri, 04 May 1753 00:00:00 +0000

As you can see, if we're accurately tracking the number of solar years since Shakespeare's birthday then the correct anniversary date would be the 4th May and not the 23rd April.

So when should you use DateTime in Ruby and when should you use Time? Almost certainly you'll want to use ::Time since your app is probably dealing with current dates and times. However, if you need to deal with dates and times in a historical context you'll want to use DateTime to avoid making the same mistakes as UNESCO. If you also have to deal with timezones then best of luck - just bear in mind that you'll probably be dealing with local solar times, since it wasn't until the 19th century that the introduction of the railways necessitated the need for Standard Time and eventually timezones.

Constant Summary

::Date - Inherited

ABBR_DAYNAMES, ABBR_MONTHNAMES, DAYNAMES, ENGLAND, GREGORIAN, ITALY, JULIAN, MONTHNAMES

Class Method Summary

::Date - Inherited

._httpdate

Returns a hash of parsed elements.
._iso8601

Returns a hash of parsed elements.
._jisx0301

Returns a hash of parsed elements.
._parse

Parses the given representation of date and time, and returns a hash of parsed elements.
._rfc2822

Alias for Date._rfc822.
._rfc3339

Returns a hash of parsed elements.
._rfc822

Returns a hash of parsed elements.
._strptime

Parses the given representation of date and time with the given template, and returns a hash of parsed elements.
._xmlschema

Returns a hash of parsed elements.
.civil

Alias for Date.new.
.commercial

Creates a date object denoting the given week date.
.gregorian_leap?

Alias for Date.leap?.
.httpdate

Creates a new ::Date object by parsing from a string according to some RFC 2616 format.
.iso8601

Creates a new ::Date object by parsing from a string according to some typical ISO 8601 formats.
.jd

Creates a date object denoting the given chronological Julian day number.
.jisx0301

Creates a new ::Date object by parsing from a string according to some typical JIS X 0301 formats.
.julian_leap?

Returns true if the given year is a leap year of the proleptic Julian calendar.
.leap?

Returns true if the given year is a leap year of the proleptic Gregorian calendar.
.new

Creates a date object denoting the given calendar date.
.ordinal

Creates a date object denoting the given ordinal date.
.parse

Parses the given representation of date and time, and creates a date object.
.rfc2822

Alias for Date.rfc822.
.rfc3339

Creates a new ::Date object by parsing from a string according to some typical RFC 3339 formats.
.rfc822

Creates a new ::Date object by parsing from a string according to some typical RFC 2822 formats.
.strptime

Parses the given representation of date and time with the given template, and creates a date object.
.today

Creates a date object denoting the present day.
.valid_civil?

Alias for Date.valid_date?.
.valid_commercial?

Returns true if the given week date is valid, and false if not.
.valid_date?

Returns true if the given calendar date is valid, and false if not.
.valid_jd?

Just returns true.
.valid_ordinal?

Returns true if the given ordinal date is valid, and false if not.
.xmlschema

Creates a new ::Date object by parsing from a string according to some typical XML Schema formats.

Instance Attribute Summary

::Date - Inherited

#friday?

Returns true if the date is Friday.
#gregorian

This method is equivalent to new_start(Date::GREGORIAN).
#gregorian?

Returns true if the date is on or after the day of calendar reform.
#julian

This method is equivalent to new_start(Date::JULIAN).
#julian?

Returns true if the date is before the day of calendar reform.
#leap?

Returns true if the year is a leap year.
#monday?

Returns true if the date is Monday.
#saturday?

Returns true if the date is Saturday.
#sunday?

Returns true if the date is Sunday.
#thursday?

Returns true if the date is Thursday.
#tuesday?

Returns true if the date is Tuesday.
#wednesday?

Returns true if the date is Wednesday.

Instance Method Summary

::Date - Inherited

#+

Returns a date object pointing other days after self.
#-

Returns the difference between the two dates if the other is a date object.
#<<

Returns a date object pointing n months before self.
#<=>

Compares the two dates and returns -1, zero, 1 or nil.
#===

Returns true if they are the same day.
#>>

Returns a date object pointing n months after self.
#ajd

Returns the astronomical Julian day number.
#amjd

Returns the astronomical modified Julian day number.
#asctime

Alias for Date#ctime.
#ctime

Returns a string in asctime(3) format (but without “n0” at the end).
#cwday

Returns the day of calendar week (1-7, Monday is 1).
#cweek

Returns the calendar week number (1-53).
#cwyear

Returns the calendar week based year.
#day

Returns the day of the month (1-31).
#day_fraction

Returns the fractional part of the day.
#downto

This method is equivalent to step(min, -1){|date| …}.
#england

This method is equivalent to new_start(Date::ENGLAND).
#httpdate

This method is equivalent to strftime('%a, %d %b %Y %T GMT').
#inspect

Returns the value as a string for inspection.
#iso8601

This method is equivalent to strftime('%F').
#italy

This method is equivalent to new_start(Date::ITALY).
#jd

Returns the Julian day number.
#jisx0301

Returns a string in a JIS X 0301 format.
#ld

Returns the Lilian day number.
#mday

Alias for Date#day.
#mjd

Returns the modified Julian day number.
#mon

Returns the month (1-12).
#month

Alias for Date#mon.
#new_start

Duplicates self and resets its day of calendar reform.
#next

Returns a date object denoting the following day.
#next_day

This method is equivalent to d + n.
#next_month

This method is equivalent to d >> n.
#next_year

This method is equivalent to d >> (n * 12).
#prev_day

This method is equivalent to d - n.
#prev_month

This method is equivalent to d << n.
#prev_year

This method is equivalent to d << (n * 12).
#rfc2822

Alias for Date#rfc822.
#rfc3339

This method is equivalent to strftime('%FT%T%:z').
#rfc822

This method is equivalent to strftime('%a, %-d %b %Y %T %z').
#start

Returns the Julian day number denoting the day of calendar reform.
#step

Iterates evaluation of the given block, which takes a date object.
#strftime

Formats date according to the directives in the given format string.
#succ

Alias for Date#next.
#to_date

Returns self.
#to_datetime

Returns a DateTime object which denotes self.
#to_s

Returns a string in an ISO 8601 format.
#to_time

Returns a ::Time object which denotes self.
#upto

This method is equivalent to step(max, 1){|date| …}.
#wday

Returns the day of week (0-6, Sunday is zero).
#xmlschema

Alias for Date#iso8601.
#yday

Returns the day of the year (1-366).
#year

Returns the year.
#hour

Returns the hour (0-23).
#min

Returns the minute (0-59).
#minute

Alias for Date#min.
#new_offset

Duplicates self and resets its offset.
#offset

Returns the offset.
#sec

Returns the second (0-59).
#sec_fraction

Returns the fractional part of the second.
#second

Alias for Date#sec.
#second_fraction

Alias for Date#sec_fraction.
#zone

Returns the timezone.

Constructor Details

.civil([year=-4712[, month=1[, mday=1[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]]]) ⇒ DateTime .new([year=-4712[, month=1[, mday=1[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]]]) ⇒ DateTime
Also known as: .civil

Creates a DateTime object denoting the given calendar date.

DateTime.new(2001,2,3)    #=> #<DateTime: 2001-02-03T00:00:00+00:00 ...>
DateTime.new(2001,2,3,4,5,6,'+7')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.new(2001,-11,-26,-20,-55,-54,'+7')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

Class Method Details

._strptime(string[, format='%FT%T%z']) ⇒ Hash

Parses the given representation of date and time with the given template, and returns a hash of parsed elements. _strptime does not support specification of flags and width unlike strftime.

See also strptime(3) and #strftime.

.civil([year=-4712[, month=1[, mday=1[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]]]) ⇒ DateTime .new([year=-4712[, month=1[, mday=1[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]]]) ⇒ DateTime

Alias for .new.

.commercial([cwyear=-4712[, cweek=1[, cwday=1[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]]]) ⇒ DateTime

Creates a DateTime object denoting the given week date.

DateTime.commercial(2001) #=> #<DateTime: 2001-01-01T00:00:00+00:00 ...>
DateTime.commercial(2002) #=> #<DateTime: 2001-12-31T00:00:00+00:00 ...>
DateTime.commercial(2001,5,6,4,5,6,'+7')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

.httpdate(string='Mon, 01 Jan -4712 00:00:00 GMT'[, start=Date::ITALY]) ⇒ DateTime

Creates a new DateTime object by parsing from a string according to some RFC 2616 format.

DateTime.httpdate('Sat, 03 Feb 2001 04:05:06 GMT')
                          #=> #<DateTime: 2001-02-03T04:05:06+00:00 ...>

.iso8601(string='-4712-01-01T00:00:00+00:00'[, start=Date::ITALY]) ⇒ DateTime

Creates a new DateTime object by parsing from a string according to some typical ISO 8601 formats.

DateTime.iso8601('2001-02-03T04:05:06+07:00')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.iso8601('20010203T040506+0700')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.iso8601('2001-W05-6T04:05:06+07:00')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

.jd([jd=0[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]) ⇒ DateTime

Creates a DateTime object denoting the given chronological Julian day number.

DateTime.jd(2451944)      #=> #<DateTime: 2001-02-03T00:00:00+00:00 ...>
DateTime.jd(2451945)      #=> #<DateTime: 2001-02-04T00:00:00+00:00 ...>
DateTime.jd(Rational('0.5'))
                          #=> #<DateTime: -4712-01-01T12:00:00+00:00 ...>

.jisx0301(string='-4712-01-01T00:00:00+00:00'[, start=Date::ITALY]) ⇒ DateTime

Creates a new DateTime object by parsing from a string according to some typical JIS X 0301 formats.

DateTime.jisx0301('H13.02.03T04:05:06+07:00')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

.now([start = Date::ITALY]) ⇒ DateTime

Creates a DateTime object denoting the present time.

DateTime.now              #=> #<DateTime: 2011-06-11T21:20:44+09:00 ...>

.ordinal([year=-4712[, yday=1[, hour=0[, minute=0[, second=0[, offset=0[, start=Date::ITALY]]]]]]]) ⇒ DateTime

Creates a DateTime object denoting the given ordinal date.

DateTime.ordinal(2001,34) #=> #<DateTime: 2001-02-03T00:00:00+00:00 ...>
DateTime.ordinal(2001,34,4,5,6,'+7')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.ordinal(2001,-332,-20,-55,-54,'+7')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

.parse(string='-4712-01-01T00:00:00+00:00'[, comp=true[, start=Date::ITALY]]) ⇒ DateTime

Parses the given representation of date and time, and creates a DateTime object. This method does not function as a validator.

If the optional second argument is true and the detected year is in the range “00” to “99”, makes it full.

DateTime.parse('2001-02-03T04:05:06+07:00')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.parse('20010203T040506+0700')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.parse('3rd Feb 2001 04:05:06 PM')
                          #=> #<DateTime: 2001-02-03T16:05:06+00:00 ...>

.rfc2822(string='Mon, 1 Jan -4712 00:00:00 +0000'[, start=Date::ITALY]) ⇒ DateTime .rfc822(string='Mon, 1 Jan -4712 00:00:00 +0000'[, start=Date::ITALY]) ⇒ DateTime

Alias for .rfc822.

.rfc3339(string='-4712-01-01T00:00:00+00:00'[, start=Date::ITALY]) ⇒ DateTime

Creates a new DateTime object by parsing from a string according to some typical RFC 3339 formats.

DateTime.rfc3339('2001-02-03T04:05:06+07:00')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

.rfc2822(string='Mon, 1 Jan -4712 00:00:00 +0000'[, start=Date::ITALY]) ⇒ DateTime .rfc822(string='Mon, 1 Jan -4712 00:00:00 +0000'[, start=Date::ITALY]) ⇒ DateTime
Also known as: .rfc2822

Creates a new DateTime object by parsing from a string according to some typical RFC 2822 formats.

DateTime.rfc2822('Sat, 3 Feb 2001 04:05:06 +0700')
                         #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

.strptime([string='-4712-01-01T00:00:00+00:00'[, format='%FT%T%z'[ ,start=Date::ITALY]]]) ⇒ DateTime

Parses the given representation of date and time with the given template, and creates a DateTime object. strptime does not support specification of flags and width unlike strftime.

DateTime.strptime('2001-02-03T04:05:06+07:00', '%Y-%m-%dT%H:%M:%S%z')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.strptime('03-02-2001 04:05:06 PM', '%d-%m-%Y %I:%M:%S %p')
                          #=> #<DateTime: 2001-02-03T16:05:06+00:00 ...>
DateTime.strptime('2001-W05-6T04:05:06+07:00', '%G-W%V-%uT%H:%M:%S%z')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.strptime('2001 04 6 04 05 06 +7', '%Y %U %w %H %M %S %z')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.strptime('2001 05 6 04 05 06 +7', '%Y %W %u %H %M %S %z')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>
DateTime.strptime('-1', '%s')
                          #=> #<DateTime: 1969-12-31T23:59:59+00:00 ...>
DateTime.strptime('-1000', '%Q')
                          #=> #<DateTime: 1969-12-31T23:59:59+00:00 ...>
DateTime.strptime('sat3feb014pm+7', '%a%d%b%y%H%p%z')
                          #=> #<DateTime: 2001-02-03T16:00:00+07:00 ...>

See also strptime(3) and #strftime.

.xmlschema(string='-4712-01-01T00:00:00+00:00'[, start=Date::ITALY]) ⇒ DateTime

Creates a new DateTime object by parsing from a string according to some typical XML Schema formats.

DateTime.xmlschema('2001-02-03T04:05:06+07:00')
                          #=> #<DateTime: 2001-02-03T04:05:06+07:00 ...>

Instance Method Details

#iso8601([n = 0]) ⇒ String #xmlschema([n = 0]) ⇒ String
Also known as: #xmlschema

This method is equivalent to strftime('%FT%T%:z'). The optional argument n is the number of digits for fractional seconds.

DateTime.parse('2001-02-03T04:05:06.123456789+07:00').iso8601(9)
                          #=> "2001-02-03T04:05:06.123456789+07:00"

#jisx0301([n = 0]) ⇒ String

Returns a string in a JIS X 0301 format. The optional argument n is the number of digits for fractional seconds.

DateTime.parse('2001-02-03T04:05:06.123456789+07:00').jisx0301(9)
                          #=> "H13.02.03T04:05:06.123456789+07:00"

#rfc3339([n = 0]) ⇒ String

This method is equivalent to strftime('%FT%T%:z'). The optional argument n is the number of digits for fractional seconds.

DateTime.parse('2001-02-03T04:05:06.123456789+07:00').rfc3339(9)
                          #=> "2001-02-03T04:05:06.123456789+07:00"

#strftime([format = '%FT%T%:z']) ⇒ String

Formats date 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.

A directive consists of a percent (%) character, zero or more flags, an optional minimum field width, an 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 (can be negative, 4 digits at least)
          -0001, 0000, 1995, 2009, 14292, etc.
  %C - year / 100 (round down.  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..59)

  %L - Millisecond of the second (000..999)
  %N - Fractional seconds digits, default is 9 digits (nanosecond)
          %3N  millisecond (3 digits)   %15N femtosecond (15 digits)
          %6N  microsecond (6 digits)   %18N attosecond  (18 digits)
          %9N  nanosecond  (9 digits)   %21N zeptosecond (21 digits)
          %12N picosecond (12 digits)   %24N yoctosecond (24 digits)

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 - hour, minute and second offset from UTC
                                            (e.g. +09, +09:30, +09:30:30)
  %Z - Equivalent to %:z (e.g. +09:00)

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 week 1 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 week 1 of YYYY 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 Unix Epoch:
  %s - Number of seconds since 1970-01-01 00:00:00 UTC.
  %Q - Number of milliseconds 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-%Y)
  %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)
  %+ - date(1) (%a %b %e %H:%M:%S %Z %Y)

This method is similar to the strftime() function defined in ISO C and POSIX. Several directives (%a, %A, %b, %B, %c, %p, %r, %x, %X, %E*, %O* and %Z) are locale dependent in the function. However, this method is locale independent. So, the result may differ even if the same format string is used in other systems such as C. It is good practice to avoid %x and %X because there are corresponding locale independent representations, %D and %T.

Examples:

d = DateTime.new(2007,11,19,8,37,48,"-06:00")
                          #=> #<DateTime: 2007-11-19T08:37:48-0600 ...>
d.strftime("Printed on %m/%d/%Y")   #=> "Printed on 11/19/2007"
d.strftime("at %I:%M%p")            #=> "at 08:37AM"

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)

See also strftime(3) and .strptime.

#to_date ⇒ date

Returns a ::Date object which denotes self.

#to_datetime ⇒ self

Returns self.

#to_s ⇒ String

Returns a string in an ISO 8601 format. (This method doesn't use the expanded representations.)

DateTime.new(2001,2,3,4,5,6,'-7').to_s
                         #=> "2001-02-03T04:05:06-07:00"

#to_time ⇒ Time

Returns a ::Time object which denotes self.

#iso8601([n = 0]) ⇒ String #xmlschema([n = 0]) ⇒ String

Alias for #iso8601.