NAME¶
DateTime::Duration - Duration objects for date math
VERSION¶
version 1.12
SYNOPSIS¶
use DateTime::Duration;
$dur = DateTime::Duration->new(
years => 3,
months => 5,
weeks => 1,
days => 1,
hours => 6,
minutes => 15,
seconds => 45,
nanoseconds => 12000
);
my ( $days, $hours, $seconds ) = $dur->in_units('days', 'hours', 'seconds');
# Human-readable accessors, always positive, but consider using
# DateTime::Format::Duration instead
$dur->years;
$dur->months;
$dur->weeks;
$dur->days;
$dur->hours;
$dur->minutes;
$dur->seconds;
$dur->nanoseconds;
$dur->is_wrap_mode
$dur->is_limit_mode
$dur->is_preserve_mode
print $dur->end_of_month_mode;
# Multiply all values by -1
my $opposite = $dur->inverse;
my $bigger = $dur1 + $dur2;
my $smaller = $dur1 - $dur2; # the result could be negative
my $bigger = $dur1 * 3;
my $base_dt = DateTime->new( year => 2000 );
my @sorted =
sort { DateTime::Duration->compare( $a, $b, $base_dt ) } @durations;
if ( $dur->is_positive ) { ... }
if ( $dur->is_zero ) { ... }
if ( $dur->is_negative ) { ... }
DESCRIPTION¶
This is a simple class for representing duration objects. These objects are used
whenever you do date math with DateTime.pm.
See the How DateTime Math Works section of the DateTime.pm documentation for
more details. The short course: One cannot in general convert between seconds,
minutes, days, and months, so this class will never do so. Instead, create the
duration with the desired units to begin with, for example by calling the
appropriate subtraction/delta method on a "DateTime.pm" object.
METHODS¶
Like "DateTime" itself, "DateTime::Duration" returns the
object from mutator methods in order to make method chaining possible.
"DateTime::Duration" has the following methods:
DateTime::Duration->new( ... )¶
This method takes the parameters "years", "months",
"weeks", "days", "hours", "minutes",
"seconds", "nanoseconds", and "end_of_month".
All of these except "end_of_month" are numbers. If any of the
numbers are negative, the entire duration is negative.
All of the numbers
must be integers.
Internally, years as just treated as 12 months. Similarly, weeks are treated as
7 days, and hours are converted to minutes. Seconds and nanoseconds are both
treated separately.
The "end_of_month" parameter must be either "wrap",
"limit", or "preserve". This parameter specifies how date
math that crosses the end of a month is handled.
In "wrap" mode, adding months or years that result in days beyond the
end of the new month will roll over into the following month. For instance,
adding one year to Feb 29 will result in Mar 1.
If you specify "end_of_month" mode as "limit", the end of
the month is never crossed. Thus, adding one year to Feb 29, 2000 will result
in Feb 28, 2001. If you were to then add three more years this will result in
Feb 28, 2004.
If you specify "end_of_month" mode as "preserve", the same
calculation is done as for "limit" except that if the original date
is at the end of the month the new date will also be. For instance, adding one
month to Feb 29, 2000 will result in Mar 31, 2000.
For positive durations, the "end_of_month" parameter defaults to wrap.
For negative durations, the default is "limit". This should match
how most people "intuitively" expect datetime math to work.
$dur->clone()¶
Returns a new object with the same properties as the object on which this method
was called.
$dur->in_units( ... )¶
Returns the length of the duration in the units (any of those that can be passed
to "new") given as arguments. All lengths are integral, but may be
negative. Smaller units are computed from what remains after taking away the
larger units given, so for example:
my $dur = DateTime::Duration->new( years => 1, months => 15 );
$dur->in_units( 'years' ); # 2
$dur->in_units( 'months' ); # 27
$dur->in_units( 'years', 'months' ); # (2, 3)
$dur->in_units( 'weeks', 'days' ); # (0, 0) !
The last example demonstrates that there will not be any conversion between
units which don't have a fixed conversion rate. The only conversions possible
are:
- •
- years <=> months
- •
- weeks <=> days
- •
- hours <=> minutes
- •
- seconds <=> nanoseconds
For the explanation of why this is the case, please see the How DateTime Math
Works section of the DateTime.pm documentation
Note that the numbers returned by this method may not match the values given to
the constructor.
In list context, in_units returns the lengths in the order of the units given.
In scalar context, it returns the length in the first unit (but still computes
in terms of all given units).
If you need more flexibility in presenting information about durations, please
take a look a "DateTime::Format::Duration".
$dur->is_positive(), $dur-> is_zero(), $dur->is_negative()¶
Indicates whether or not the duration is positive, zero, or negative.
If the duration contains both positive and negative units, then it will return
false for
all of these methods.
$dur->is_wrap_mode(), $dur-> is_limit_mode(), $dur->is_preserve_mode()¶
Indicates what mode is used for end of month wrapping.
$dur->end_of_month_mode()¶
Returns one of "wrap", "limit", or "preserve".
$dur->calendar_duration()¶
Returns a new object with the same
calendar delta (months and days only)
and end of month mode as the current object.
$dur->clock_duration()¶
Returns a new object with the same
clock deltas (minutes, seconds, and
nanoseconds) and end of month mode as the current object.
$dur->inverse( ... )¶
Returns a new object with the same deltas as the current object, but multiple by
-1. The end of month mode for the new object will be the default end of month
mode, which depends on whether the new duration is positive or negative.
You can set the end of month mode in the inverted duration explicitly by passing
"end_of_month => ..." to the "inverse()" method.
$dur->add_duration( $duration_object ), $dur->subtract_duration( $duration_object )¶
Adds or subtracts one duration from another.
$dur->add( ... ), $dur->subtract( ... )¶
Syntactic sugar for addition and subtraction. The parameters given to these
methods are used to create a new object, which is then passed to
"add_duration()" or "subtract_duration()", as appropriate.
$dur->multiply( $number )¶
Multiplies each unit in the by the specified number.
DateTime::Duration->compare( $duration1, $duration2, $base_datetime )¶
This is a class method that can be used to compare or sort durations. Comparison
is done by adding each duration to the specified "DateTime.pm"
object and comparing the resulting datetimes. This is necessary because
without a base, many durations are not comparable. For example, 1 month may or
may not be longer than 29 days, depending on what datetime it is added to.
If no base datetime is given, then the result of "DateTime->now" is
used instead. Using this default will give non-repeatable results if used to
compare two duration objects containing different units. It will also give
non-repeatable results if the durations contain multiple types of units, such
as months and days.
However, if you know that both objects only consist of one type of unit (months
or days
or hours, etc.), and each duration contains the same
type of unit, then the results of the comparison will be repeatable.
$dur->delta_months(), $dur-> delta_days(), $dur->delta_minutes(), $dur->delta_seconds(), $dur-> delta_nanoseconds()¶
These methods provide the information "DateTime.pm" needs for doing
date math. The numbers returned may be positive or negative. This is mostly
useful for doing date math in DateTime.
$dur->deltas()¶
Returns a hash with the keys "months", "days",
"minutes", "seconds", and "nanoseconds",
containing all the delta information for the object. This is mostly useful for
doing date math in DateTime.
$dur->years(), $dur-> months(), $dur->weeks(), $dur->days(), $dur-> hours(), $dur->minutes(), $dur->seconds(), $dur-> nanoseconds()¶
These methods return numbers indicating how many of the given unit the object
represents, after having done a conversion to any larger units. For example,
days are first converted to weeks, and then the remainder is returned. These
numbers are always positive.
Here's what each method returns:
$dur->years() == abs( $dur->in_units('years') )
$dur->months() == abs( ( $dur->in_units( 'months', 'years' ) )[0] )
$dur->weeks() == abs( $dur->in_units( 'weeks' ) )
$dur->days() == abs( ( $dur->in_units( 'days', 'weeks' ) )[0] )
$dur->hours() == abs( $dur->in_units( 'hours' ) )
$dur->minutes == abs( ( $dur->in_units( 'minutes', 'hours' ) )[0] )
$dur->seconds == abs( $dur->in_units( 'seconds' ) )
$dur->nanoseconds() == abs( ( $dur->in_units( 'nanoseconds', 'seconds' ) )[0] )
If this seems confusing, remember that you can always use the
"in_units()" method to specify exactly what you want.
Better yet, if you are trying to generate output suitable for humans, use the
"DateTime::Format::Duration" module.
Overloading¶
This class overloads addition, subtraction, and mutiplication.
Comparison is
not overloaded. If you attempt to compare durations using
"<=>" or "cmp", then an exception will be thrown!
Use the "compare()" class method instead.
SUPPORT¶
Support for this module is provided via the datetime@perl.org email list. See
http://lists.perl.org/ for more details.
SEE ALSO¶
datetime@perl.org mailing list
http://datetime.perl.org/
AUTHOR¶
Dave Rolsky <autarch@urth.org>
COPYRIGHT AND LICENSE¶
This software is Copyright (c) 2014 by Dave Rolsky.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)