DateTime::Format::Pg(3pm)				User Contributed Perl Documentation				 DateTime::Format::Pg(3pm)

NAME

       DateTime::Format::Pg - Parse and format PostgreSQL dates and times

SYNOPSIS

	 use DateTime::Format::Pg;

	 my $dt = DateTime::Format::Pg->parse_datetime( '2003-01-16 23:12:01' );

	 # 2003-01-16T23:12:01+0200
	 DateTime::Format::Pg->format_datetime($dt);

DESCRIPTION

       This module understands the formats used by PostgreSQL for its DATE, TIME, TIMESTAMP, and INTERVAL data types.  It can be used to parse
       these formats in order to create "DateTime" or "DateTime::Duration" objects, and it can take a "DateTime" or "DateTime::Duration" object
       and produce a string representing it in a format accepted by PostgreSQL.

CONSTRUCTORS

       The following methods can be used to create "DateTime::Format::Pg" objects.

       o   new( name => value, ... )

	   Creates a new "DateTime::Format::Pg" instance. This is generally not required for simple operations. If you wish to use a different
	   parsing style from the default then it is more comfortable to create an object.

	     my $parser = DateTime::Format::Pg->new()
	     my $copy = $parser->new( 'european' => 1 );

	   This method accepts the following options:

	   o	   european

		   If european is set to non-zero, dates are assumed to be in european dd/mm/yyyy format. The default is to assume US mm/dd/yyyy
		   format (because this is the default for PostgreSQL).

		   This option only has an effect if PostgreSQL is set to output dates in the 'PostgreSQL' (DATE only) and 'SQL' (DATE and
		   TIMESTAMP) styles.

		   Note that you don't have to set this option if the PostgreSQL server has been set to use the 'ISO' format, which is the
		   default.

	   o	   server_tz

		   This option can be set to a "DateTime::TimeZone" object or a string that contains a time zone name.

		   This value must be set to the same value as the PostgreSQL server's time zone in order to parse TIMESTAMP WITH TIMEZONE values
		   in the 'PostgreSQL', 'SQL', and 'German' formats correctly.

		   Note that you don't have to set this option if the PostgreSQL server has been set to use the 'ISO' format, which is the
		   default.

       o   clone()

	   This method is provided for those who prefer to explicitly clone via a method called "clone()".

	      my $clone = $original->clone();

	   If called as a class method it will die.

METHODS

       This class provides the following methods. The parse_datetime, parse_duration, format_datetime, and format_duration methods are general-
       purpose methods provided for compatibility with other "DateTime::Format" modules.

       The other methods are specific to the corresponding PostgreSQL date/time data types. The names of these methods are derived from the name
       of the PostgreSQL data type.  (Note: Prior to PostgreSQL 7.3, the TIMESTAMP type was equivalent to the TIMESTAMP WITH TIME ZONE type. This
       data type corresponds to the format/parse_timestamp_with_time_zone method but not to the format/parse_timestamp method.)

   PARSING METHODS
       This class provides the following parsing methods.

       As a general rule, the parsing methods accept input in any format that the PostgreSQL server can produce. However, if PostgreSQL's
       DateStyle is set to 'SQL' or 'PostgreSQL', dates can only be parsed correctly if the 'european' option is set correctly (i.e. same as the
       PostgreSQL server).  The same is true for time zones and the 'australian_timezones' option in all modes but 'ISO'.

       The default DateStyle, 'ISO', will always produce unambiguous results and is also parsed most efficiently by this parser class. I stronlgly
       recommend using this setting unless you have a good reason not to.

       o   parse_datetime($string,...)

	   Given a string containing a date and/or time representation, this method will return a new "DateTime" object.

	   If the input string does not contain a date, it is set to 1970-01-01.  If the input string does not contain a time, it is set to
	   00:00:00.  If the input string does not contain a time zone, it is set to the floating time zone.

	   If given an improperly formatted string, this method may die.

       o   parse_timestamptz($string,...)

       o   parse_timestamp_with_time_zone($string,...)

	   Given a string containing a timestamp (date and time) representation, this method will return a new "DateTime" object. This method is
	   suitable for the TIMESTAMPTZ (or TIMESTAMP WITH TIME ZONE) type.

	   If the input string does not contain a time zone, it is set to the floating time zone.

	   Please note that PostgreSQL does not actually store a time zone along with the TIMESTAMP WITH TIME ZONE (or TIMESTAMPTZ) type but will
	   just return a time stamp converted for the server's local time zone.

	   If given an improperly formatted string, this method may die.

       o   parse_timestamp($string,...)

       o   parse_timestamp_without_time_zone($string,...)

	   Similar to the functions above, but always returns a "DateTime" object with a floating time zone. This method is suitable for the
	   TIMESTAMP (or TIMESTAMP WITHOUT TIME ZONE) type.

	   If the server does return a time zone, it is ignored.

	   If given an improperly formatted string, this method may die.

       o   parse_timetz($string,...)

       o   parse_time_with_time_zone($string,...)

	   Given a string containing a time representation, this method will return a new "DateTime" object. The date is set to 1970-01-01. This
	   method is suitable for the TIMETZ (or TIME WITH TIME ZONE) type.

	   If the input string does not contain a time zone, it is set to the floating time zone.

	   Please note that PostgreSQL stores a numerical offset with its TIME WITH TIME ZONE (or TIMETZ) type. It does not store a time zone name
	   (such as 'Europe/Rome').

	   If given an improperly formatted string, this method may die.

       o   parse_time($string,...)

       o   parse_time_without_time_zone($string,...)

	   Similar to the functions above, but always returns an "DateTime" object with a floating time zone. If the server returns a time zone,
	   it is ignored. This method is suitable for use with the TIME (or TIME WITHOUT TIME ZONE) type.

	   This ensures that the resulting "DateTime" object will always have the time zone expected by your application.

	   If given an improperly formatted string, this method may die.

       o   parse_date($string,...)

	   Given a string containing a date representation, this method will return a new "DateTime" object. The time is set to 00:00:00 (floating
	   time zone). This method is suitable for the DATE type.

	   If given an improperly formatted string, this method may die.

       o   parse_duration($string)

       o   parse_interval($string)

	   Given a string containing a duration (SQL type INTERVAL) representation, this method will return a new "DateTime::Duration" object.

	   If given an improperly formatted string, this method may die.

   FORMATTING METHODS
       This class provides the following formatting methods.

       The output is always in the format mandated by the SQL standard (derived from ISO 8601), which is parsed by PostgreSQL unambiguously in all
       DateStyle modes.

       o   format_datetime($datetime,...)

	   Given a "DateTime" object, this method returns a string appropriate as input for all date and date/time types of PostgreSQL. It will
	   contain date and time.

	   If the time zone of the "DateTime" part is floating, the resulting string will contain no time zone, which will result in the server's
	   time zone being used. Otherwise, the numerical offset of the time zone is used.

       o   format_time($datetime,...)

       o   format_time_without_time_zone($datetime,...)

	   Given a "DateTime" object, this method returns a string appropriate as input for the TIME type (also known as TIME WITHOUT TIME ZONE),
	   which will contain the local time of the "DateTime" object and no time zone.

       o   format_timetz($datetime)

       o   format_time_with_time_zone($datetime)

	   Given a "DateTime" object, this method returns a string appropriate as input for the TIME WITH TIME ZONE type (also known as TIMETZ),
	   which will contain the local part of the "DateTime" object and a numerical time zone.

	   You should not use the TIME WITH TIME ZONE type to store dates with floating time zones.  If the time zone of the "DateTime" part is
	   floating, the resulting string will contain no time zone, which will result in the server's time zone being used.

       o   format_date($datetime)

	   Given a "DateTime" object, this method returns a string appropriate as input for the DATE type, which will contain the date part of the
	   "DateTime" object.

       o   format_timestamp($datetime)

       o   format_timestamp_without_time_zone($datetime)

	   Given a "DateTime" object, this method returns a string appropriate as input for the TIMESTAMP type (also known as TIMESTAMP WITHOUT
	   TIME ZONE), which will contain the local time of the "DateTime" object and no time zone.

       o   format_timestamptz($datetime)

       o   format_timestamp_with_time_zone($datetime)

	   Given a "DateTime" object, this method returns a string appropriate as input for the TIMESTAMP WITH TIME ZONE type, which will contain
	   the local part of the "DateTime" object and a numerical time zone.

	   You should not use the TIMESTAMP WITH TIME ZONE type to store dates with floating time zones.  If the time zone of the "DateTime" part
	   is floating, the resulting string will contain no time zone, which will result in the server's time zone being used.

       o   format_duration($du)

       o   format_interval($du)

	   Given a "DateTime::Duration" object, this method returns a string appropriate as input for the INTERVAL type.

LIMITATIONS

       Some output formats of PostgreSQL have limitations that can only be passed on by this class.

       As a general rules, none of these limitations apply to the 'ISO' output format.	It is strongly recommended to use this format (and to use
       PostgreSQL's to_char function when another output format that's not supposed to be handled by a parser of this class is desired). 'ISO' is
       the default but you are advised to explicitly set it at the beginnig of the session by issuing a SET DATESTYLE TO 'ISO'; command in case
       the server administrator changes that setting.

       When formatting DateTime objects, this class always uses a format that's handled unambiguously by PostgreSQL.

   TIME ZONES
       If DateStyle is set to 'PostgreSQL', 'SQL', or 'German', PostgreSQL does not send numerical time zones for the TIMESTAMPTZ (or TIMESTAMP
       WITH TIME ZONE) type. Unfortunatly, the time zone names used instead can be ambiguous: For example, 'EST' can mean -0500, +1000, or +1100.

       You must set the 'server_tz' variable to a time zone that is identical to that of the PostgreSQL server. If the server is set to a
       different time zone (or the underlying operating system interprets the time zone differently), the parser will return wrong times.

       You can avoid such problems by setting the server's time zone to UTC using the SET TIME ZONE 'UTC' command and setting 'server_tz'
       parameter to 'UTC' (or by using the ISO output format, of course).

   EUROPEAN DATES
       For the SQL (for DATE and TIMSTAMP[TZ]) and the PostgreSQL (for DATE) output format, the server can send dates in both European-style
       'dd/mm/yyyy' and in US-style 'mm/dd/yyyy' format. In order to parse these dates correctly, you have to pass the 'european' option to the
       constructor or to the "parse_xxx" routines.

       This problem does not occur when using the ISO or German output format (and for PostgreSQL with TIMESTAMP[TZ] as month names are used
       then).

   INTERVAL ELEMENTS
       "DateTime::Duration" stores months, days, minutes and seconds separately. PostgreSQL only stores months and seconds and disregards the
       irregular length of days due to DST switching and the irregular length of minutes due to leap seconds. Therefore, it is not possitble to
       store "DateTime::Duration" objects as SQL INTERVALs without the loss of some information.

   NEGATIVE INTERVALS
       In the SQL and German output formats, the server does not send an indication of the sign with intervals. This means that '1 month ago' and
       '1 month' are both returned as '1 mon'.

       This problem can only be avoided by using the 'ISO' or 'PostgreSQL' output format.

SUPPORT

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

AUTHOR

       Daisuke Maki <daisuke@endeworks.jp>

AUTHOR EMERITUS

       Claus A. Faerber <perl@faerber.muc.de>

COPYRIGHT

       Copyright (c) 2003 Claus A. Faerber. Copyright (c) 2005-2007 Daisuke Maki

       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/

perl v5.14.2							    2011-11-25						 DateTime::Format::Pg(3pm)