Date::Simple(3) User Contributed Perl Documentation Date::Simple(3)NAMEDate::Simple - a simple date object
SYNOPSIS
use Date::Simple ('date', 'today');
# Difference in days between two dates:
$diff = date('2001-08-27') - date('1977-10-05');
# Offset $n days from now:
$date = today() + $n;
print "$date\n"; # uses ISO 8601 format (YYYY-MM-DD)
use Date::Simple ();
my $date = Date::Simple->new('1972-01-17');
my $year = $date->year;
my $month = $date->month;
my $day = $date->day;
use Date::Simple (':all');
my $date2 = ymd($year, $month, $day);
my $date3 = d8('19871218');
my $today = today();
my $tomorrow = $today + 1;
if ($tomorrow->year != $today->year) {
print "Today is New Year's Eve!\n";
}
if ($today > $tomorrow) {
die "warp in space-time continuum";
}
print "Today is ";
print(('Sun','Mon','Tues','Wednes','Thurs','Fri','Satur')
[$today->day_of_week]);
print "day.\n";
# you can also do this:
($date cmp "2001-07-01")
# and this
($date <=> [2001, 7, 1])
DESCRIPTION
Dates are complex enough without times and timezones. This module may
be used to create simple date objects. It handles:
Validation.
Reject 1999-02-29 but accept 2000-02-29.
Interval arithmetic.
How many days were between two given dates? What date comes N days
after today?
Day-of-week calculation.
What day of the week is a given date?
Transparent date formatting.
How should a date object be formatted.
It does not deal with hours, minutes, seconds, and time zones.
A date is uniquely identified by year, month, and day integers within
valid ranges. This module will not allow the creation of objects for
invalid dates. Attempting to create an invalid date will return undef.
Month numbering starts at 1 for January, unlike in C and Java. Years
are 4-digit.
Gregorian dates up to year 9999 are handled correctly, but we rely on
Perl's builtin "localtime" function when the current date is requested.
On some platforms, "localtime" may be vulnerable to rollovers such as
the Unix "time_t" wraparound of 18 January 2038.
Overloading is used so you can compare or subtract two dates using
standard numeric operators such as "==", and the sum of a date object
and an integer is another date object.
Date::Simple objects are immutable. After assigning $date1 to $date2,
no change to $date1 can affect $date2. This means, for example, that
there is nothing like a "set_year" operation, and "$date++" assigns a
new object to $date.
This module contains various undocumented functions. They may not be
available on all platforms and are likely to change or disappear in
future releases. Please let the author know if you think any of them
should be public.
Controlling output format.
As of version 3.0 new ways of controlling the output formats of
Date::Simple objects has been provided. However Date::Simple has
traditionally provided few ways of stringification, a primary one via
the format() method and another primary one via direct stringification.
However the later is currently implemented as an XS routine and the
former is implemented through a perl routine. This means that using
format() is more expensive than stringification and that the
stringification format is class specific.
In order to alleviate some of these problems a new mechanism has been
introduced to Date::Simple that allows for a per object level format
default. In addition a set of utility classes that have different
stringification overloads provided. These classes are simple
subclasses of Date::Simple and beside the default format() and the
overloaded stringification behaviour are identical to Date::Simple. In
fact one is totally identical to Date::Simple and is provided mostly
for completeness.
The classes included are:
Date::Simple::ISO
Identical to Date::Simple in every respect but name.
Date::Simple::D8
Uses the D8 format (%Y%m%d) as the default format for printing.
Uses XS for the overloaded stringification.
Date::Simple::Fmt
Uses the perl implemented format() as the default stringification
mechanism. The first argument to the constructor is expected to be
the format to use for the object.
NOTE its important to remember that the primary difference between the
behaviour of objects of the different classes is how they are
stringified when quoted, and what date format is used by default when
the format() method is called. Nothing else differs.
CONSTRUCTORS
Several functions take a string or numeric representation and generate
a corresponding date object. The most general is "new", whose argument
list may be empty (returning the current date), a string in format
YYYY-MM-DD or YYYYMMDD, a list or arrayref of year, month, and day
number, or an existing date object.
Date::Simple->new ([ARG, ...])
date ([ARG, ...])
my $date = Date::Simple->new('1972-01-17');
The "new" method will return a date object if the values passed in
specify a valid date. (See above.) If an invalid date is passed,
the method returns undef. If the argument is invalid in form as
opposed to numeric range, "new" dies.
The "date" function provides the same functionality but must be
imported or qualified as "Date::Simple::date". (To import all
public functions, do "use Date::Simple (':all');".) This function
returns undef on all invalid input, rather than dying in some cases
like "new".
date_fmt (FMT,[ARG, ...])
Equivelent to "date" but creates a Date::Simple::Fmt object
instead. The format is expected to be a valid POSIX::strftime
format string.
date_iso ([ARG, ...])
Identical to "date" but creates a Date::Simple::ISO object instead.
date_d8 ([ARG, ...])
Equivelent to "date" but creates a Date::Simple::D8 object instead.
today()
Returns the current date according to "localtime".
Caution: To get tomorrow's date (or any fixed offset from today),
do not use "today + 1". Perl parses this as "today(+1)". You need
to put empty parentheses after the function: "today() + 1".
ymd (YEAR, MONTH, DAY)
Returns a date object with the given year, month, and day numbers.
If the arguments do not specify a valid date, undef is returned.
Example:
use Date::Simple ('ymd');
$pbd = ymd(1987, 12, 18);
d8 (STRING)
Parses STRING as "YYYYMMDD" and returns the corresponding date
object, or undef if STRING has the wrong format or specifies an
invalid date.
Example:
use Date::Simple ('d8');
$doi = d8('17760704');
Mnemonic: The string matches "/\d{8}/". Also, "d8" spells "date",
if 8 is expanded phonetically.
INSTANCE METHODS
DATE->next
my $tomorrow = $today->next;
Returns an object representing tomorrow.
DATE->prev
my $yesterday = $today->prev;
Returns an object representing yesterday.
DATE->year
my $year = $date->year;
Return the year of DATE as an integer.
DATE->month
my $month = $date->month;
Return the month of DATE as an integer from 1 to 12.
DATE->day
my $day = $date->day;
Return the DATE's day of the month as an integer from 1 to 31.
DATE->day_of_week
Return a number representing DATE's day of the week from 0 to 6,
where 0 means Sunday.
DATE->as_ymd
my ($year, $month, $day) = $date->as_ymd;
Returns a list of three numbers: year, month, and day.
DATE->as_d8
Returns the "d8" representation (see "d8"), like
"$date->format("%Y%m%d")".
DATE->as_iso
Returns the ISO 8601 representation of the date (eg '2004-01-01'),
like "$date->format("%Y-%m-%d")". This is in fact the default
overloaded stringification mechanism and is provided mostly so
other subclasses with different overloading can still do fast ISO
style date output.
DATE->as_str ([STRING])
DATE->format ([STRING])
DATE->strftime ([STRING])
These functions are equivalent. Return a string representing the
date, in the format specified. If you don't pass a parameter, the
default date format for the object is used if one has been
specified, otherwise uses the default date format for the class the
object is a member of, or as a last fallback uses the
$Date::Simple::Standard_Format which is changeable, but probably
shouldn't be modified. See "default_format" for details.
my $change_date = $date->format("%d %b %y");
my $iso_date1 = $date->format("%Y-%m-%d");
my $iso_date2 = $date->format;
The formatting parameter is similar to one you would pass to
strftime(3). This is because we actually do pass it to strftime to
format the date. This may result in differing behavior across
platforms and locales and may not even work everywhere.
DATE->default_format ([FORMAT])
This method sets or gets the default_format for the DATE object or
class that it is called on.
OPERATORS
Some operators can be used with Date::Simple instances. If one side of
an expression is a date object, and the operator expects two date
objects, the other side is interpreted as "date(ARG)", so an array
reference or ISO 8601 string will work.
DATE + NUMBER
DATE - NUMBER
You can construct a new date offset by a number of days using the
"+" and "-" operators.
DATE1 - DATE2
You can subtract two dates to find the number of days between them.
DATE1 == DATE2
DATE1 < DATE2
DATE1 <=> DATE2
DATE1 cmp DATE2
etc.
You can compare two dates using the arithmetic or string comparison
operators. Equality tests ("==" and "eq") return false when one of
the expressions can not be converted to a date. Other comparison
tests die in such cases. This is intentional, because in a sense,
all non-dates are not "equal" to all dates, but in no sense are
they "greater" or "less" than dates.
DATE += NUMBER
DATE -= NUMBER
You can increment or decrement a date by a number of days using the
+= and -= operators. This actually generates a new date object and
is equivalent to "$date = $date + $number".
"$date"
You can interpolate a date instance directly into a string, in the
format specified by ISO 8601 (eg: 2000-01-17) for Date::Simple and
Date::Simple::ISO, for Date::Simple::D8 this is the same as calling
as_d8() on the object, and for Date::Simple::Fmt this is the same
as calling format() on the object.
UTILITIES
leap_year (YEAR)
Returns true if YEAR is a leap year.
days_in_month (YEAR, MONTH)
Returns the number of days in MONTH, YEAR.
leap_year (YEAR)
Returns true if YEAR is a leap year.
days_in_month (YEAR, MONTH)
Returns the number of days in MONTH, YEAR.
AUTHOR
Marty Pauley <marty@kasei.com>
John Tobey <jtobey@john-edwin-tobey.org>
Yves Orton <demerphq@hotmail.com>
COPYRIGHT
Copyright (C) 2001 Kasei.
Copyright (C) 2001,2002 John Tobey.
Copyright (C) 2004 Yves Orton.
This program is free software; you can redistribute it and/or
modify it under the terms of either:
a) the GNU General Public License;
either version 2 of the License, or (at your option) any later
version. You should have received a copy of the GNU General
Public License along with this program; see the file COPYING.
If not, write to the Free Software Foundation, Inc., 59
Temple Place, Suite 330, Boston, MA 02111-1307 USA
b) the Perl Artistic License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO
Date::Simple::Fmt Date::Simple::ISO Date::Simple::D8 and of course perl
perl v5.14.0 2008-12-26 Date::Simple(3)