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Class: Date

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses:
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, Comparable
Inherits: Object
Defined in: ext/date/date_core.c,
ext/date/lib/date.rb

Overview

date and datetime class - Tadayoshi Funaba 1998-2011

'date' provides two classes: Date and ::Time.

Terms and Definitions

Some terms and definitions are based on ISO 8601 and JIS X 0301.

Calendar Date

The calendar date is a particular day of a calendar year, identified by its ordinal number within a calendar month within that year.

In those classes, this is so-called “civil”.

Ordinal Date

The ordinal date is a particular day of a calendar year identified by its ordinal number within the year.

In those classes, this is so-called “ordinal”.

Week Date

The week date is a date identified by calendar week and day numbers.

The calendar week is a seven day period within a calendar year, starting on a Monday and identified by its ordinal number within the year; the first calendar week of the year is the one that includes the first Thursday of that year. In the Gregorian calendar, this is equivalent to the week which includes January 4.

In those classes, this is so-called “commercial”.

Julian Day Number

The Julian day number is in elapsed days since noon (Greenwich Mean ::Time) on January 1, 4713 BCE (in the Julian calendar).

In this document, the astronomical Julian day number is the same as the original Julian day number. And the chronological Julian day number is a variation of the Julian day number. Its days begin at midnight on local time.

In this document, when the term “Julian day number” simply appears, it just refers to “chronological Julian day number”, not the original.

In those classes, those are so-called “ajd” and “jd”.

Modified Julian Day Number

The modified Julian day number is in elapsed days since midnight (Coordinated Universal Time) on November 17, 1858 CE (in the Gregorian calendar).

In this document, the astronomical modified Julian day number is the same as the original modified Julian day number. And the chronological modified Julian day number is a variation of the modified Julian day number. Its days begin at midnight on local time.

In this document, when the term “modified Julian day number” simply appears, it just refers to “chronological modified Julian day number”, not the original.

In those classes, those are so-called “amjd” and “mjd”.

Date

A subclass of ::Object that includes the Comparable module and easily handles date.

A Date object is created with .new, .jd, .ordinal, .commercial, .parse, .strptime, .today, Time#to_date, etc.

require 'date'

Date.new(2001,2,3)
 #=> #<Date: 2001-02-03 ...>
Date.jd(2451944)
 #=> #<Date: 2001-02-03 ...>
Date.ordinal(2001,34)
 #=> #<Date: 2001-02-03 ...>
Date.commercial(2001,5,6)
 #=> #<Date: 2001-02-03 ...>
Date.parse('2001-02-03')
 #=> #<Date: 2001-02-03 ...>
Date.strptime('03-02-2001', '%d-%m-%Y')
 #=> #<Date: 2001-02-03 ...>
Time.new(2001,2,3).to_date
 #=> #<Date: 2001-02-03 ...>

All date objects are immutable; hence cannot modify themselves.

The concept of a date object can be represented as a tuple of the day count, the offset and the day of calendar reform.

The day count denotes the absolute position of a temporal dimension. The offset is relative adjustment, which determines decoded local time with the day count. The day of calendar reform denotes the start day of the new style. The old style of the West is the Julian calendar which was adopted by Caesar. The new style is the Gregorian calendar, which is the current civil calendar of many countries.

The day count is virtually the astronomical Julian day number. The offset in this class is usually zero, and cannot be specified directly.

A Date object can be created with an optional argument, the day of calendar reform as a Julian day number, which should be 2298874 to 2426355 or negative/positive infinity. The default value is ITALY (2299161=1582-10-15). See also sample/cal.rb.

$ ruby sample/cal.rb -c it 10 1582
    October 1582
 S  M Tu  W Th  F  S
    1  2  3  4 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31

$ ruby sample/cal.rb -c gb  9 1752
   September 1752
 S  M Tu  W Th  F  S
       1  2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

A Date object has various methods. See each reference.

d = Date.parse('3rd Feb 2001')
                             #=> #<Date: 2001-02-03 ...>
d.year                       #=> 2001
d.mon                        #=> 2
d.mday                       #=> 3
d.wday                       #=> 6
d += 1                       #=> #<Date: 2001-02-04 ...>
d.strftime('%a %d %b %Y')    #=> "Sun 04 Feb 2001"

Constant Summary

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.civil([year=-4712[, month=1[, mday=1[, start=Date::ITALY]]]]) ⇒ Date .new([year=-4712[, month=1[, mday=1[, start=Date::ITALY]]]]) ⇒ Date
Also known as: .civil

Creates a date object denoting the given calendar date.

In this class, BCE years are counted astronomically. Thus, the year before the year 1 is the year zero, and the year preceding the year zero is the year -1. The month and the day of month should be a negative or a positive number (as a relative month/day from the end of year/month when negative). They should not be zero.

The last argument should be a Julian day number which denotes the day of calendar reform. ITALY (2299161=1582-10-15), ENGLAND (2361222=1752-09-14), GREGORIAN (the proleptic Gregorian calendar) and JULIAN (the proleptic Julian calendar) can be specified as a day of calendar reform.

Date.new(2001)            #=> #<Date: 2001-01-01 ...>
Date.new(2001,2,3)        #=> #<Date: 2001-02-03 ...>
Date.new(2001,2,-1)       #=> #<Date: 2001-02-28 ...>

See also .jd.

Class Method Details

._httpdate(string) ⇒ Hash

Returns a hash of parsed elements.

._iso8601(string) ⇒ Hash

Returns a hash of parsed elements.

._jisx0301(string) ⇒ Hash

Returns a hash of parsed elements.

._parse(string[, comp=true]) ⇒ Hash

Parses the given representation of date and time, and returns a hash of parsed elements. 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”, considers the year a 2-digit form and makes it full.

Date._parse('2001-02-03') #=> {:year=>2001, :mon=>2, :mday=>3}

._rfc2822(string) ⇒ Hash ._rfc822(string) ⇒ Hash

Alias for ._rfc822.

._rfc3339(string) ⇒ Hash

Returns a hash of parsed elements.

._rfc2822(string) ⇒ Hash ._rfc822(string) ⇒ Hash
Also known as: ._rfc2822

Returns a hash of parsed elements.

._strptime(string[, format='%F']) ⇒ 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.

Date._strptime('2001-02-03', '%Y-%m-%d')
                          #=> {:year=>2001, :mon=>2, :mday=>3}

See also strptime(3) and #strftime.

._xmlschema(string) ⇒ Hash

Returns a hash of parsed elements.

.civil([year=-4712[, month=1[, mday=1[, start=Date::ITALY]]]]) ⇒ Date .new([year=-4712[, month=1[, mday=1[, start=Date::ITALY]]]]) ⇒ Date

Alias for .new.

.commercial([cwyear=-4712[, cweek=1[, cwday=1[, start=Date::ITALY]]]]) ⇒ Date

Creates a date object denoting the given week date.

The week and the day of week should be a negative or a positive number (as a relative week/day from the end of year/week when negative). They should not be zero.

Date.commercial(2001)     #=> #<Date: 2001-01-01 ...>
Date.commercial(2002)     #=> #<Date: 2001-12-31 ...>
Date.commercial(2001,5,6) #=> #<Date: 2001-02-03 ...>

See also .jd and .new.

.gregorian_leap?(year) ⇒ Boolean .leap?(year) ⇒ Boolean

Alias for .leap?.

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

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

Date.httpdate('Sat, 03 Feb 2001 00:00:00 GMT')
                                          #=> #<Date: 2001-02-03 ...>

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

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

Date.iso8601('2001-02-03')        #=> #<Date: 2001-02-03 ...>
Date.iso8601('20010203')          #=> #<Date: 2001-02-03 ...>
Date.iso8601('2001-W05-6')        #=> #<Date: 2001-02-03 ...>

.jd([jd=0[, start=Date::ITALY]]) ⇒ Date

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

Date.jd(2451944)          #=> #<Date: 2001-02-03 ...>
Date.jd(2451945)          #=> #<Date: 2001-02-04 ...>
Date.jd(0)                #=> #<Date: -4712-01-01 ...>

See also .new.

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

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

Date.jisx0301('H13.02.03')                #=> #<Date: 2001-02-03 ...>

.julian_leap?(year) ⇒ Boolean

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

Date.julian_leap?(1900)           #=> true
Date.julian_leap?(1901)           #=> false

.gregorian_leap?(year) ⇒ Boolean .leap?(year) ⇒ Boolean
Also known as: .gregorian_leap?

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

Date.gregorian_leap?(1900)        #=> false
Date.gregorian_leap?(2000)        #=> true

.ordinal([year=-4712[, yday=1[, start=Date::ITALY]]]) ⇒ Date

Creates a date object denoting the given ordinal date.

The day of year should be a negative or a positive number (as a relative day from the end of year when negative). It should not be zero.

Date.ordinal(2001)        #=> #<Date: 2001-01-01 ...>
Date.ordinal(2001,34)     #=> #<Date: 2001-02-03 ...>
Date.ordinal(2001,-1)     #=> #<Date: 2001-12-31 ...>

See also .jd and .new.

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

Parses the given representation of date and time, and creates a date 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”, considers the year a 2-digit form and makes it full.

Date.parse('2001-02-03')          #=> #<Date: 2001-02-03 ...>
Date.parse('20010203')            #=> #<Date: 2001-02-03 ...>
Date.parse('3rd Feb 2001')        #=> #<Date: 2001-02-03 ...>

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

Alias for .rfc822.

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

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

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

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

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

Date.rfc2822('Sat, 3 Feb 2001 00:00:00 +0000')
                                          #=> #<Date: 2001-02-03 ...>

.strptime([string='-4712-01-01'[, format='%F'[, start=Date::ITALY]]]) ⇒ Date

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

Date.strptime('2001-02-03', '%Y-%m-%d')   #=> #<Date: 2001-02-03 ...>
Date.strptime('03-02-2001', '%d-%m-%Y')   #=> #<Date: 2001-02-03 ...>
Date.strptime('2001-034', '%Y-%j')        #=> #<Date: 2001-02-03 ...>
Date.strptime('2001-W05-6', '%G-W%V-%u')  #=> #<Date: 2001-02-03 ...>
Date.strptime('2001 04 6', '%Y %U %w')    #=> #<Date: 2001-02-03 ...>
Date.strptime('2001 05 6', '%Y %W %u')    #=> #<Date: 2001-02-03 ...>
Date.strptime('sat3feb01', '%a%d%b%y')    #=> #<Date: 2001-02-03 ...>

See also strptime(3) and #strftime.

.today([start = Date::ITALY]) ⇒ Date

Creates a date object denoting the present day.

Date.today   #=> #<Date: 2011-06-11 ...>

.valid_civil?(year, month, mday[, start=Date::ITALY]) ⇒ Boolean .valid_date?(year, month, mday[, start=Date::ITALY]) ⇒ Boolean

Alias for .valid_date?.

.valid_commercial?(cwyear, cweek, cwday[, start=Date::ITALY]) ⇒ Boolean

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

Date.valid_commercial?(2001,5,6)  #=> true
Date.valid_commercial?(2001,5,8)  #=> false

See also .jd and .commercial.

.valid_civil?(year, month, mday[, start=Date::ITALY]) ⇒ Boolean .valid_date?(year, month, mday[, start=Date::ITALY]) ⇒ Boolean
Also known as: .valid_civil?

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

Date.valid_date?(2001,2,3)        #=> true
Date.valid_date?(2001,2,29)       #=> false

See also .jd and .civil.

.valid_jd?(jd[, start=Date::ITALY]) ⇒ Boolean

Just returns true. It's nonsense, but is for symmetry.

Date.valid_jd?(2451944)           #=> true

See also .jd.

.valid_ordinal?(year, yday[, start=Date::ITALY]) ⇒ Boolean

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

Date.valid_ordinal?(2001,34)      #=> true
Date.valid_ordinal?(2001,366)     #=> false

See also .jd and .ordinal.

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

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

Date.xmlschema('2001-02-03')      #=> #<Date: 2001-02-03 ...>

Instance Attribute Details

#friday?Boolean (readonly)

Returns true if the date is Friday.

#gregorianDate (readonly)

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

#gregorian?Boolean (readonly)

Retunrs true if the date is on or after the day of calendar reform.

Date.new(1582,10,15).gregorian?          #=> true
(Date.new(1582,10,15) - 1).gregorian?    #=> false

#julianDate (readonly)

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

#julian?Boolean (readonly)

Retruns true if the date is before the day of calendar reform.

Date.new(1582,10,15).julian?             #=> false
(Date.new(1582,10,15) - 1).julian?       #=> true

#leap?Boolean (readonly)

Returns true if the year is a leap year.

Date.new(2000).leap?      #=> true
Date.new(2001).leap?      #=> false

#monday?Boolean (readonly)

Returns true if the date is Monday.

#saturday?Boolean (readonly)

Returns true if the date is Saturday.

#sunday?Boolean (readonly)

Returns true if the date is Sunday.

#thursday?Boolean (readonly)

Returns true if the date is Thursday.

#tuesday?Boolean (readonly)

Returns true if the date is Tuesday.

#wednesday?Boolean (readonly)

Returns true if the date is Wednesday.

Instance Method Details

#+(other) ⇒ Date

Returns a date object pointing other days after self. The other should be a numeric value. If the other is a fractional number, assumes its precision is at most nanosecond.

Date.new(2001,2,3) + 1    #=> #<Date: 2001-02-04 ...>
DateTime.new(2001,2,3) + Rational(1,2)
                          #=> #<DateTime: 2001-02-03T12:00:00+00:00 ...>
DateTime.new(2001,2,3) + Rational(-1,2)
                          #=> #<DateTime: 2001-02-02T12:00:00+00:00 ...>
DateTime.jd(0,12) + DateTime.new(2001,2,3).ajd
                          #=> #<DateTime: 2001-02-03T00:00:00+00:00 ...>

#-(other) ⇒ Date, Rational

Returns the difference between the two dates if the other is a date object. If the other is a numeric value, returns a date object pointing other days before self. If the other is a fractional number, assumes its precision is at most nanosecond.

Date.new(2001,2,3) - 1   #=> #<Date: 2001-02-02 ...>
DateTime.new(2001,2,3) - Rational(1,2)
                         #=> #<DateTime: 2001-02-02T12:00:00+00:00 ...>
Date.new(2001,2,3) - Date.new(2001)
                         #=> (33/1)
DateTime.new(2001,2,3) - DateTime.new(2001,2,2,12)
                         #=> (1/2)

#<<(n) ⇒ Date

Returns a date object pointing n months before self. The argument n should be a numeric value.

Date.new(2001,2,3)  <<  1   #=> #<Date: 2001-01-03 ...>
Date.new(2001,2,3)  << -2   #=> #<Date: 2001-04-03 ...>

When the same day does not exist for the corresponding month, the last day of the month is used instead:

Date.new(2001,3,28) << 1   #=> #<Date: 2001-02-28 ...>
Date.new(2001,3,31) << 1   #=> #<Date: 2001-02-28 ...>

This also results in the following, possibly unexpected, behavior:

Date.new(2001,3,31) << 2         #=> #<Date: 2001-01-31 ...>
Date.new(2001,3,31) << 1 << 1    #=> #<Date: 2001-01-28 ...>

Date.new(2001,3,31) << 1 << -1   #=> #<Date: 2001-03-28 ...>

#<=>(other) ⇒ 1, ...

Compares the two dates and returns -1, zero, 1 or nil. The other should be a date object or a numeric value as an astronomical Julian day number.

Date.new(2001,2,3) <=> Date.new(2001,2,4)   #=> -1
Date.new(2001,2,3) <=> Date.new(2001,2,3)   #=> 0
Date.new(2001,2,3) <=> Date.new(2001,2,2)   #=> 1
Date.new(2001,2,3) <=> Object.new           #=> nil
Date.new(2001,2,3) <=> Rational(4903887,2)  #=> 0

See also Comparable.

#===(other) ⇒ Boolean

Returns true if they are the same day.

Date.new(2001,2,3) === Date.new(2001,2,3)
                                  #=> true
Date.new(2001,2,3) === Date.new(2001,2,4)
                                  #=> false
DateTime.new(2001,2,3) === DateTime.new(2001,2,3,12)
                                  #=> true
DateTime.new(2001,2,3) === DateTime.new(2001,2,3,0,0,0,'+24:00')
                                  #=> true
DateTime.new(2001,2,3) === DateTime.new(2001,2,4,0,0,0,'+24:00')
                                  #=> false

#>>(n) ⇒ Date

Returns a date object pointing n months after self. The argument n should be a numeric value.

Date.new(2001,2,3)  >>  1   #=> #<Date: 2001-03-03 ...>
Date.new(2001,2,3)  >> -2   #=> #<Date: 2000-12-03 ...>

When the same day does not exist for the corresponding month, the last day of the month is used instead:

Date.new(2001,1,28) >> 1   #=> #<Date: 2001-02-28 ...>
Date.new(2001,1,31) >> 1   #=> #<Date: 2001-02-28 ...>

This also results in the following, possibly unexpected, behavior:

Date.new(2001,1,31) >> 2         #=> #<Date: 2001-03-31 ...>
Date.new(2001,1,31) >> 1 >> 1    #=> #<Date: 2001-03-28 ...>

Date.new(2001,1,31) >> 1 >> -1   #=> #<Date: 2001-01-28 ...>

#ajdRational

Returns the astronomical Julian day number. This is a fractional number, which is not adjusted by the offset.

DateTime.new(2001,2,3,4,5,6,'+7').ajd     #=> (11769328217/4800)
DateTime.new(2001,2,2,14,5,6,'-7').ajd    #=> (11769328217/4800)

#amjdRational

Returns the astronomical modified Julian day number. This is a fractional number, which is not adjusted by the offset.

DateTime.new(2001,2,3,4,5,6,'+7').amjd    #=> (249325817/4800)
DateTime.new(2001,2,2,14,5,6,'-7').amjd   #=> (249325817/4800)

#asctimeString #ctimeString

Alias for #ctime.

#asctimeString #ctimeString
Also known as: #asctime

Returns a string in asctime(3) format (but without “n0” at the end). This method is equivalent to strftime('%c').

See also asctime(3) or ctime(3).

#cwdayFixnum

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

Date.new(2001,2,3).cwday          #=> 6

#cweekFixnum

Returns the calendar week number (1-53).

Date.new(2001,2,3).cweek          #=> 5

#cwyearInteger

Returns the calendar week based year.

Date.new(2001,2,3).cwyear         #=> 2001
Date.new(2000,1,1).cwyear         #=> 1999

#mdayFixnum #dayFixnum
Also known as: #mday

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

Date.new(2001,2,3).mday           #=> 3

#day_fractionRational

Returns the fractional part of the day.

DateTime.new(2001,2,3,12).day_fraction    #=> (1/2)

#downto(min) ⇒ Enumerator #downto(min) {|date| ... } ⇒ self

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

#englandDate

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

#hourFixnum (private)

Returns the hour (0-23).

DateTime.new(2001,2,3,4,5,6).hour         #=> 4

#httpdateString

This method is equivalent to strftime('%a, %d %b %Y %T GMT'). See also RFC 2616.

#inspectString

Returns the value as a string for inspection.

Date.new(2001,2,3).inspect
          #=> "#<Date: 2001-02-03 ((2451944j,0s,0n),+0s,2299161j)>"
DateTime.new(2001,2,3,4,5,6,'-7').inspect
          #=> "#<DateTime: 2001-02-03T04:05:06-07:00 ((2451944j,39906s,0n),-25200s,2299161j)>"

#iso8601String #xmlschemaString
Also known as: #xmlschema

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

#italyDate

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

#jdInteger

Returns the Julian day number. This is a whole number, which is adjusted by the offset as the local time.

DateTime.new(2001,2,3,4,5,6,'+7').jd      #=> 2451944
DateTime.new(2001,2,3,4,5,6,'-7').jd      #=> 2451944

#jisx0301String

Returns a string in a JIS X 0301 format.

Date.new(2001,2,3).jisx0301       #=> "H13.02.03"

#ldInteger

Returns the Lilian day number. This is a whole number, which is adjusted by the offset as the local time.

Date.new(2001,2,3).ld            #=> 152784

#mdayFixnum #dayFixnum

Alias for #day.

#minFixnum (private) #minuteFixnum
Also known as: #minute

Returns the minute (0-59).

DateTime.new(2001,2,3,4,5,6).min          #=> 5

#minFixnum (private) #minuteFixnum

Alias for #min.

#mjdInteger

Returns the modified Julian day number. This is a whole number, which is adjusted by the offset as the local time.

DateTime.new(2001,2,3,4,5,6,'+7').mjd     #=> 51943
DateTime.new(2001,2,3,4,5,6,'-7').mjd     #=> 51943

#monFixnum #monthFixnum
Also known as: #month

Returns the month (1-12).

Date.new(2001,2,3).mon            #=> 2

#monFixnum #monthFixnum

Alias for #mon.

#new_offset([offset = 0]) ⇒ Date (private)

Duplicates self and resets its offset.

d = DateTime.new(2001,2,3,4,5,6,'-02:00')
                          #=> #<DateTime: 2001-02-03T04:05:06-02:00 ...>
d.new_offset('+09:00')    #=> #<DateTime: 2001-02-03T15:05:06+09:00 ...>

#new_start([start = Date::ITALY]) ⇒ Date

Duplicates self and resets its day of calendar reform.

d = Date.new(1582,10,15)
d.new_start(Date::JULIAN)         #=> #<Date: 1582-10-05 ...>

#succDate #nextDate
Also known as: #succ

Returns a date object denoting the following day.

#next_day([n = 1]) ⇒ Date

This method is equivalent to d + n.

#next_month([n = 1]) ⇒ Date

This method is equivalent to d >> n.

See #>> for examples.

#next_year([n = 1]) ⇒ Date

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

Date.new(2001,2,3).next_year      #=> #<Date: 2002-02-03 ...>
Date.new(2008,2,29).next_year     #=> #<Date: 2009-02-28 ...>
Date.new(2008,2,29).next_year(4)  #=> #<Date: 2012-02-29 ...>

See also #>>.

#offsetRational (private)

Returns the offset.

DateTime.parse('04pm+0730').offset        #=> (5/16)

#prev_day([n = 1]) ⇒ Date

This method is equivalent to d - n.

#prev_month([n = 1]) ⇒ Date

This method is equivalent to d << n.

See #<< for examples.

#prev_year([n = 1]) ⇒ Date

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

Date.new(2001,2,3).prev_year      #=> #<Date: 2000-02-03 ...>
Date.new(2008,2,29).prev_year     #=> #<Date: 2007-02-28 ...>
Date.new(2008,2,29).prev_year(4)  #=> #<Date: 2004-02-29 ...>

See also #<<.

#rfc2822String #rfc822String

Alias for #rfc822.

#rfc3339String

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

#rfc2822String #rfc822String
Also known as: #rfc2822

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

#secFixnum (private) #secondFixnum
Also known as: #second

Returns the second (0-59).

DateTime.new(2001,2,3,4,5,6).sec          #=> 6

#sec_fractionRational (private) #second_fractionRational
Also known as: #second_fraction

Returns the fractional part of the second.

DateTime.new(2001,2,3,4,5,6.5).sec_fraction       #=> (1/2)

#secFixnum (private) #secondFixnum

Alias for #sec.

#sec_fractionRational (private) #second_fractionRational

Alias for #sec_fraction.

#startFloat

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

Date.new(2001,2,3).start                  #=> 2299161.0
Date.new(2001,2,3,Date::GREGORIAN).start  #=> -Infinity

#step(limit[, step=1]) ⇒ Enumerator #step(limit[, step=1]) {|date| ... } ⇒ self

Iterates evaluation of the given block, which takes a date object. The limit should be a date object.

Date.new(2001).step(Date.new(2001,-1,-1)).select{|d| d.sunday?}.size
                          #=> 52

#strftime([format = '%F']) ⇒ 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.

The minimum field width specifies the minimum width.

The modifiers are “E”, “O”, “:”, “::” and “:::”. “E” and “O” are ignored. No effect to result currently.

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 - Time zone abbreviation name or something similar information.

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.

#succDate #nextDate

Alias for #next.

#to_dateself

Returns self;

#to_datetimeDate

Returns a ::Time object which denotes self.

#to_sString

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

Date.new(2001,2,3).to_s  #=> "2001-02-03"

#to_timeTime

Returns a ::Time object which denotes self.

#upto(max) ⇒ Enumerator #upto(max) {|date| ... } ⇒ self

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

#wdayFixnum

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

Date.new(2001,2,3).wday           #=> 6

#iso8601String #xmlschemaString

Alias for #iso8601.

#ydayFixnum

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

Date.new(2001,2,3).yday           #=> 34

#yearInteger

Returns the year.

Date.new(2001,2,3).year           #=> 2001
(Date.new(1,1,1) - 1).year        #=> 0

#zoneString (private)

Returns the timezone.

DateTime.parse('04pm+0730').zone          #=> "+07:30"