DateTime::Incomplete(3)

NAME
DateTime::Incomplete - An incomplete datetime, like January 5

SYNOPSIS
  my $dti = DateTime::Incomplete->new( year => 2003 );
  # 2003-xx-xx
  $dti->set( month => 12 );
  # 2003-12-xx
  $dt = $dti->to_datetime( base => DateTime->now );
  # 2003-12-19T16:54:33

DESCRIPTION
DateTime::Incomplete is a class for representing partial dates and times.

These are actually encountered relatively frequently. For example, a birthday is commonly given as a month and day, without a year.

ERROR HANDLING
Constructor and mutator methods (such as "new" and "set") will die if there is an attempt to set the datetime to an invalid value.

Invalid values are detected by setting the appropriate fields of a "base" datetime object. See the "set_base" method.

Accessor methods (such as day()) will return either a value or "undef", but will never die.

THE "BASE" DATETIME
A "DateTime::Incomplete" object can have a "base" "DateTime.pm" object. This object is used as a default datetime in the to_datetime() method, and it also used to validate inputs to the set() method.

The base object must use the year/month/day system. Most calendars use this system including Gregorian ("DateTime") and Julian. Note that this module has not been well tested with base objects from classes other than "DateTime.pm" class.

By default, newly created "DateTime::Incomplete" objects have no base.

DATETIME-LIKE METHODS
Most methods provided by this class are designed to emulate the behavior of "DateTime.pm" whenever possible.

•   new()

    Creates a new incomplete date:

      my $dti = DateTime::Incomplete->new( year => 2003 );
      # 2003-xx-xx

    This class method accepts parameters for each date and time component: "year", "month", "day", "hour", "minute", "second", "nanosecond". Additionally, it accepts "time_zone", "locale", and "base" parameters.

    Any parameters not given default to "undef".

    Calling the new() method without parameters creates a completely undefined datetime:

      my $dti = DateTime::Incomplete->new();

•   from_day_of_year( ... )

    This constructor takes the same arguments as can be given to the new() method, except that it does not accept a "month" or "day" argument. Instead, it requires both "year" and "day_of_year". The day of year must be between 1 and 366, and 366 is only allowed for leap years.

    It creates a "DateTime::Incomplete" object with all date fields defined, but with the time fields (hour, minute, etc.) set to undef.

•   from_object( object => $object, ... )

    This class method can be used to construct a new "DateTime::Incomplete" object from any object that implements the utc_rd_values() method. All "DateTime::Calendar" modules must implement this method in order to provide cross-calendar compatibility. This method accepts a "locale" parameter.

    If the object passed to this method has a time_zone() method, that is used to set the time zone. Otherwise UTC is used.

    It creates a "DateTime::Incomplete" object with all fields defined.

•   from_epoch( ... )

    This class method can be used to construct a new "DateTime::Incomplete" object from an epoch time instead of components. Just as with the new() method, it accepts "time_zone" and "locale" parameters.

    If the epoch value is not an integer, the part after the decimal will be converted to nanoseconds. This is done in order to be compatible with "Time::HiRes".

    It creates a "DateTime::Incomplete" object with all fields defined.

•   now( ... )

    This class method is equivalent to "DateTime->now".

    It creates a new "DateTime::Incomplete" object with all fields defined.

•   today( ... )

    This class method is equivalent to now(), but it leaves hour, minute, second and nanosecond undefined.

•   clone

    Creates a new object with the same information as the object this method is called on.

  "Get" Methods

•   year

•   month

•   day

•   hour

•   minute

•   second

•   nanosecond

•   time_zone

•   locale

    These methods returns the field value for the object, or "undef".

    These values can also be accessed using the same alias methods available in "DateTime.pm", such as mon(), mday(), etc.

•   has_year

•   has_month

•   has_day

•   has_hour

•   has_minute

•   has_second

•   has_nanosecond

•   has_time_zone

•   has_locale

•   has_date

•   has_time

    Returns a boolean value indicating whether the corresponding component is defined.

    "has_date" tests for year, month, and day.

    "has_time" tests for hour, minute, and second.

•   has

        $has_date = $dti->has( 'year', 'month', 'day' );

    Returns a boolean value indicating whether all fields in the argument list are defined.

•   defined_fields

        @fields = $dti->defined_fields;   # list of field names

    Returns a list containing the names of the fields that are defined.

    The list order is: year, month, day, hour, minute, second, nanosecond, time_zone, locale.

•   datetime, ymd, date, hms, time, iso8601, mdy, dmy

    These are equivalent to DateTime stringification methods with the same name, except that the undefined fields are replaced by 'xx' or 'xxxx' as appropriate.

•   epoch

•   hires_epoch

•   is_dst

•   utc_rd_values

•   utc_rd_as_seconds

        my $epoch = $dti->epoch( base => $dt );

    These methods are equivalent to the "DateTime" methods with the same name.

    They all accept a "base" argument to use in order to calculate the method's return values.

    If no "base" argument is given, then "today" is used.

•   is_finite, is_infinite

    Incomplete dates are always "finite".

•   strftime( $format, ... )

    This method implements functionality similar to the strftime() method in C. However, if given multiple format strings, then it will return multiple scalars, one for each format string.

    See the "strftime Specifiers" section in the "DateTime.pm" documentation for a list of all possible format specifiers.

    Undefined fields are replaced by 'xx' or 'xxxx' as appropriate.

    The specification %s (epoch) is calculated using "today" as the base date, unless the object has a base datetime set.

Computed Values

All other accessors, such as day_of_week(), or week_year() are computed from the base values for a datetime. When these methods are called, they return the requested information if there is enough data to compute them, otherwise they return "undef"

Unimplemented Methods

The following "DateTime.pm" methods are not implemented in "DateTime::Incomplete", though some of them may be implemented in future versions:

•   add_duration

•   add

•   subtract_duration

•   subtract

•   subtract_datetime

•   subtract_datetime_absolute

•   delta_md

•   delta_days

•   delta_ms

•   compare

•   compare_ignore_floating

•   DefaultLanguage

  "Set" Methods

•   set

    Use this to set or undefine a datetime field:

      $dti->set( month => 12 );
      $dti->set( day => 24 );
      $dti->set( day => undef );

    This method takes the same arguments as the set() method in "DateTime.pm", but it can accept "undef" for any value.

•   set_time_zone

    This method accepts either a time zone object or a string that can be passed as the "name" parameter to "DateTime::TimeZone->new()".

    Unlike with "DateTime.pm", if the new time zone's offset is different from the previous time zone, no local time adjustment is made.

    You can remove time zone information by calling this method with the value "undef".

•   truncate( to => ... )

    This method allows you to reset some of the local time components in the object to their "zero" values. The "to" parameter is used to specify which values to truncate, and it may be one of "year", "month", "day", "hour", "minute", or "second". For example, if "month" is specified, then the local day becomes 1, and the hour, minute, and second all become 0.

    Note that the "to" parameter cannot be "week".

"DATETIME::INCOMPLETE" METHODS
"DateTime::Incomplete" objects also have a number of methods unique to this class.

•   base

    Returns the base datetime value, or "undef" if the object has none.

•   has_base

    Returns a boolean value indicating whether or not the object has a base datetime set.

•   is_undef

    Returns true if the datetime is completely undefined.

•   can_be_datetime

    Returns true if the datetime has enough information to be converted to a proper DateTime object.

    The year field must be valid, followed by a sequence of valid fields.

    Examples:

      Can be datetime:
      2003-xx-xxTxx:xx:xx
      2003-10-xxTxx:xx:xx
      2003-10-13Txx:xx:xx

      Can not be datetime:
      2003-10-13Txx:xx:30
      xxxx-10-13Txx:xx:30

•   set_base

    Sets the base datetime object for the "DateTime::Incomplete" object.

    The default value for "base" is "undef", which means no validation is made on input.

•   to_datetime

    This method takes an optional "base" parameter and returns a "complete" datetime.

      $dt = $dti->to_datetime( base => DateTime->now );

      $dti->set_base( DateTime->now );
      $dt = $dti->to_datetime;

    The resulting datetime can be either before of after the given base datetime. No adjustments are made, besides setting the missing fields.

    This method will use "today" if the object has no base datetime set and none is given as an argument.

    This method may die if it results in a datetime that doesn't actually exist, such as February 30, for example.

    The fields in the resulting datetime are set in this order: locale, time_zone, nanosecond, second, minute, hour, day, month, year.

•   to_recurrence

    This method generates the set of all possible datetimes that fit into an incomplete datetime definition.

      $dti = DateTime::Incomplete->new( month => 12, day => 24 );
      $dtset1 = $dti->to_recurrence;
      # Christmas recurrence, with _seconds_ resolution

      $dti->truncate( to => 'day' );
      $dtset2 = $dti->to_recurrence;
      # Christmas recurrence, with days resolution (hour/min/sec = 00:00:00)

    Those recurrences are "DateTime::Set" objects:

      $dt_next_xmas = $dti->to_recurrence->next( DateTime->today );

    Incomplete dates that have the year defined will generate finite sets. This kind of set can take a lot of resources (RAM and CPU). The following incomplete datetime would generate the set of all seconds in 2003:

      2003-xx-xxTxx:xx:xx

    Recurrences are generated with up to 1 second resolution. The "nanosecond" value is ignored.

•   to_spanset

    This method generates the set of all possible spans that fit into an incomplete datetime definition.

      $dti = DateTime::Incomplete->new( month => 12, day => 24 );
      $dtset1 = $dti->to_spanset;
      # Christmas recurrence, from xxxx-12-24T00:00:00
      #                         to xxxx-12-25T00:00:00

•   start

•   end

•   to_span

    These methods view an incomplete datetime as a "time span".

    For example, the incomplete datetime "2003-xx-xxTxx:xx:xx" starts in "2003-01-01T00:00:00" and ends in "2004-01-01T00:00:00".

    The "to_span" method returns a "DateTime::Span" object.

    An incomplete datetime without an year spans "forever". Start and end datetimes are "undef".

•   contains

    Returns a true value if the incomplete datetime range contains a given datetime value.

    For example:

      2003-xx-xx contains 2003-12-24
      2003-xx-xx does not contain 1999-12-14

•   previous / next / closest

      $dt2 = $dti->next( $dt );

    The next() returns the first complete date after or equal to the given datetime.

    The previous() returns the first complete date before or equal to the given datetime.

    The closest() returns the closest complete date (previous or next) to the given datetime.

    All of these methods return "undef" if there is no matching complete datetime.

    If no datetime is given, these methods use the "base" datetime.

    Note: The definition of previous() and next() is different from the methods of the same name in the "DateTime::Set" class.

    The datetimes are generated with 1 nanosecond precision. The last "time" value of a given day is 23:59:59.999999999 (for non leapsecond days).

SUPPORT
Support for this module is provided via the datetime@perl.org email list. See http://lists.perl.org/ for more details.

AUTHORS
Flavio S. Glock <fglock[at]cpan.org>

With Ben Bennett <fiji[at]ayup.limey.net>, Claus Farber <claus[at]xn--frber-gra.muc.de>, Dave Rolsky <autarch[at]urth.org>, Eugene Van Der Pijll <pijll[at]gmx.net>, Rick Measham <rick[at]isite.net.au>, and the DateTime team.

COPYRIGHT
Copyright (c) 2003 Flavio S. Glock. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

SEE ALSO
datetime@perl.org mailing list

http://datetime.perl.org/