Date::ICal(3)

NAME
Date::ICal - Perl extension for ICalendar date objects.

VERSION
$Revision: 678 $

SYNOPSIS
    use Date::ICal;

    $ical = Date::ICal->new( ical => '19971024T120000' );
    $ical = Date::ICal->new( epoch => time );
    $ical = Date::ICal->new( year => 1964,
        month => 10, day => 16, hour => 16,
        min => 12, sec => 47 );

    $hour = $ical->hour;
    $year = $ical->year;

    $ical_string = $ical->ical;
    $epoch_time = $ical->epoch;

    $ical2 = $ical + $duration;

(Where $duration is either a duration string, like 'P2W3DT7H9M', or a Date::ICal::Duration (qv) object.

    $ical += 'P6DT12H';

    $duration = $ical - $ical2;
    $ical3 = $ical - $duration;

DESCRIPTION
Date::ICal talks the ICal date format, and is intended to be a base class for other date/calendar modules that know about ICal time format also.

AUTHOR
Rich Bowen, and the Reefknot team. Alas, Reefknot is no more. See http://datetime.perl.org/ for more modern and accurate modules.

Last touched by $Author: rbowen $

METHODS
Date::ICal has the following methods available:

  new
A new Date::ICal object can be created with any valid ICal string:

    my $ical = Date::ICal->new( ical => '19971024T120000' );
    # will default to the timezone specified in $TZ, see below

Or with any epoch time:

    my $ical = Date::ICal->new( epoch => time );

Or, better still, create it with components

    my $date = Date::ICal->new(
                           day => 25,
                           month => 10,
                           year => 1066,
                           hour => 7,
                           min => 15,
                           sec => 47
                           );

If you call new without any arguments, you'll get a Date::ICal object that is set to the time right now.

    my $ical = Date::ICal->new();

If you already have an object in Date::ICal, or some other subclass thereof, you can create a new Date::ICal (or subclass) object using that object to start with. This is particularly useful for converting from one calendar to another:

   # Direct conversion from Discordian to ISO dates
   my $disco = Date::Discordian->new( disco => '12 Chaos, YOLD 3177' );
   my $iso = Date::ISO->new( $disco );
   print $iso->iso;

new() handles timezones. It defaults times to UTC (Greenwich Mean Time, also called Zulu). If you want to set up a time that's in the US "Pacific" timezone, which is GMT-8, use something like:

    my $ical = Date::ICal->new( ical => '19971024T120000',
                                offset => "-0800");

Note that as of version 1.44, new() tries to be intelligent about figuring out your local time zone. If you enter a time that's not *explicitly* in UTC, it looks at the environment variable $TZ, if it exists, to determine your local offset. If $TZ isn't set, new() will complain.

  ical
    $ical_string = $ical->ical;

Retrieves, or sets, the date on the object, using any valid ICal date/time string. Output is in UTC (ends with a "Z") by default. To get output in localtime relative to the current machine, do:

    $ical_string = $ical->ical( localtime => 1 );

To get output relative to an arbitrary offset, do:

    $ical_string = $ical->ical( offset => '+0545' );

  epoch
    $epoch_time = $ical->epoch;

    $ical->epoch( 98687431 );

Sets, or retrieves, the epoch time represented by the object, if it is representable as such. (Dates before 1971 or after 2038 will not have an epoch representation.)

Internals note: The ICal representation of the date is considered the only authoritative one. This means that we may need to reconstruct the epoch time from the ICal representation if we are not sure that they are in synch. We'll need to do clever things to keep track of when the two may not be in synch. And, of course, the same will go for any subclasses of this class.

  offset_to_seconds
    $seconds_plus_or_minus = offset_to_seconds($offset);

Changes -0600 to -21600. Not object method, no side-effects.

  offset_from_seconds
    $seconds_plus_or_minus = offset_from_seconds($offset_in_seconds);

Changes -18000 (seconds) to -0600 (hours, minutes). Not object method, no side-effects.

  offset
    $offset = $ical->offset;

    # We need tests for these.
    $ical->offset( '+1100' ); # a number of hours and minutes: UTC+11
    $ical->offset( 0 );       # reset to UTC

Sets or retrieves the offset from UTC for this time. This allows timezone support, assuming you know what your local (or non-local) UTC offset is. Defaults to 0.

Internals note: all times are internally stored in UTC, even though they may have some offset information. Offsets are internally stored in signed integer seconds.

BE CAREFUL about using this function on objects that were initialized with an offset. If you started an object with:

    my $d = new(ical=>'19700101120000', offset=>'+0100');

and you then call:

    $d->offset('+0200');

you'll be saying "Yeah, I know I *said* it was in +0100, but really I want it to be in +0200 now and forever." Which may be your intention, if you're trying to transpose a whole set of dates to another timezone--- but you can also do that at the presentation level, with the ical() method. Either way will work.

  add
    $self->add( year => 3, month => 2, week => 1, day => 12,
                hour => 1, minute => 34, sec => 59 );
    $date->add( duration => 'P1WT1H1M1S' ); # add 1 wk, 1 hr, 1 min, and 1 sec

Adds a duration to a Date::ICal object.

Supported paraters are: duration, eom_mode, year, month, week, day, hour, min, sec or seconds.

'duration' is a ICalendar duration string (see duration_value).

If a value is undefined or omitted, 1 is assumed:

    $ical->add( 'minute' ); # add a minute

The result will be normalized. That is, the output time will have meaningful values, rather than being 48:73 pm on the 34th of hexadecember.

Adding months or years can be done via three different methods, specified by the eom_mode parameter, which then applies to all additions (or subtractions) of months or years following it in the parameter list.

The default, eom_mode => 'wrap', means 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 eom_mode => 'limit', the end of the month is never crossed. Thus, adding one year to Feb 29, 2000 will result in Feb 28, 2001. However, adding three more years will result in Feb 28, 2004, not Feb 29.

If you specify eom_mode => '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.

All additions are performed in the order specified. For instance, with the default setting of eom_mode => 'wrap', adding one day and one month to Feb 29 will result in Apr 1, while adding one month and one day will result in Mar 30.

  add_overload
    $date = $date1 + $duration;

Where $duration is either a duration string, or a Date::ICal::Duration object.

    $date += 'P2DT4H7M';

Adds a duration to a date object. Returns a new object, or, in the case of +=, modifies the existing object.

  duration_value
Given a duration string, this function returns the number of days, seconds, and months represented by that duration. In that order. Seems odd to me. This should be considered an internal function, and you should expect the API to change in the very near future.

  subtract
  $duration = $date1 - $date2;

Subtract one Date::ICal object from another to give a duration - the length of the interval between the two dates. The return value is a Date::ICal::Duration object (qv) and allows you to get at each of the individual components, or the entire duration string:

    $d = $date1 - $X;

Note that $X can be any of the following:

If $X is another Date::ICal object (or subclass thereof) then $d will be a Date::ICal::Duration object.

    $week = $d->weeks; # how many weeks apart?
    $days = $d->as_days; # How many days apart?

If $X is a duration string, or a Date::ICal::Diration object, then $d will be an object in the same class as $date1;

    $newdate = $date - $duration;

  clone
    $copy = $date->clone;

Returns a replica of the date object, including all attributes.

  compare
    $cmp = $date1->compare($date2);

    @dates = sort {$a->compare($b)} @dates;

Compare two Date::ICal objects. Semantics are compatible with sort; returns -1 if $a < $b, 0 if $a == $b, 1 if $a > $b.

  day
    my $day = $date->day;

Returns the day of the month.

Day is in the range 1..31

  month
    my $month = $date->month;

Returns the month of the year.

Month is returned as a number in the range 1..12

  year
    my $year = $date->year;

Returns the year.

  jd2greg
    ($year, $month, $day) = jd2greg( $jd );

    Convert number of days on or after Jan 1, 1 CE (Gregorian) to
    gregorian year,month,day.

  greg2jd
    $jd = greg2jd( $year, $month, $day );

    Convert gregorian year,month,day to days on or after Jan 1, 1 CE
    (Gregorian).  Normalization is performed (e.g. month of 28 means
    April two years after given year) for month < 1 or > 12 or day < 1
    or > last day of month.

  days_this_year
  $yday = Date::ICal::days_this_year($day, $month, $year);

Returns the number of days so far this year. Analogous to the yday attribute of gmtime (or localtime) except that it works outside of the epoch.

  day_of_week
    my $day_of_week = $date->day_of_week

Returns the day of week as 0..6 (0 is Sunday, 6 is Saturday).

  hour
    my $hour = $date->hour

Returns the hour of the day.

Hour is in the range 0..23

  min
    my $min = $date->min;

Returns the minute.

Minute is in the range 0..59

  sec
    my $sec = $date->sec;

Returns the second.

Second is in the range 0..60. The value of 60 is (maybe) needed for leap seconds. But I'm not sure if we're going to go there.

  julian
  my $jd = $date->jd;

Returns a listref, containing two elements. The date as a julian day, and the time as the number of seconds since midnight. This should not be thought of as a real julian day, because it's not. The module is internally consistent, and that's enough.

This method really only is here for compatibility with previous versions, as the jd method is now thrown over for plain hash references.

See the file INTERNALS for more information about this internal format.

TODO

- add gmtime and localtime methods, perhaps?
- Fix the INTERNALS file so that it actually reflects reality

INTERNALS
Please see the file INTERNALS for discussion on the internals.

AUTHOR
Rich Bowen (DrBacchus) rbowen@rcbowen.com

And the rest of the Reefknot team. See the source for a full list of patch contributors and version-by-version notes.

SEE ALSO
datetime@perl.org mailing list

http://datetime.perl.org/

Time::Local

Net::ICal