# Copyright (c) 1995-2017 Sullivan Beck. All rights reserved. # This program is free software; you can redistribute it and/or modify it # under the same terms as Perl itself. =pod =head1 NAME Date::Manip::Examples - examples of how to use Date::Manip =head1 DESCRIPTION This document includes a number of examples on how to do common Date::Manip operations. I will be happy to add new examples over time, and welcome suggestions and examples to include. In most cases, an example will include two different ways of getting the answer. The first way will be using the new (as of 6.00) OO modules. The second will be using the old-style functional interface. It should be noted that any time you want to work with alternate time zones, the OO interface is STRONGLY recommended since the functional interface does not preserve time zone information with the date, and may therefore give incorrect results in some cases. However, working in the time zone of the system should give correct results. It should be noted that, in the examples below, it appears that the OO method often requires more lines of code than the functional interface. There are a number of ways to shorten the OO method, but for the examples, I wanted to include all the steps explicitly. =head1 PARSING A DATE Dates can be parsed in practically any form in common usage: =over 4 =item B $date = new Date::Manip::Date; $err = $date->parse("today"); $err = $date->parse("1st Thursday in June 1992"); $err = $date->parse("05/10/93"); $err = $date->parse("12:30 Dec 12th 1880"); $err = $date->parse("8:00pm December tenth"); =item B $date = ParseDate("today"); $date = ParseDate("1st Thursday in June 1992"); $date = ParseDate("05/10/93"); $date = ParseDate("12:30 Dec 12th 1880"); $date = ParseDate("8:00pm December tenth"); =back The L manual has a list of all valid formats. =head1 PARSING AN AMOUNT OF TIME Amounts of time (referred to as deltas) can also be parsed: =over 4 =item B $delta = new Date::Manip::Delta; $err = $delta->parse("in 12 hours"); $err = $delta->parse("-1:30:0"); $err = $delta->parse("4 business days later"); =item B $delta = ParseDateDelta("in 12 hours"); $delta = ParseDateDelta("-1:30:0"); $delta = ParseDateDelta("4 business days later"); =back =head1 TO CALCULATE THE AMOUNT OF TIME BETWEEN TWO DATES $datestr1 = "Jan 30 1999 13:00 EST"; $datestr2 = "2/Mar/1999 15:30:00 +0500"; =over 4 =item B $date1 = new Date::Manip::Date; $date2 = $date1->new_date(); $err = $date1->parse($datestr1); $err = $date2->parse($datestr2); To get an exact amount of time between the two dates (expressed only in terms of weeks, days, hours, minutes, seconds), use: $delta = $date1->calc($date2); To get an approximate amount of time (expressed in terms of years, months, weeks, etc. in terms that a human would typically think of), use: $delta = $date1->calc($date2,"approx"); =item B $date1 = ParseDate($string1); $date2 = ParseDate($string2); To get an exact amount: $delta = DateCalc($date1,$date2); and the approximate amount: $delta = DateCalc($date1,$date2,1); =back The L manual has information about these, and other types of calculations. =head1 TO ADD AN AMOUNT OF TIME TO A DATE To find a second date a given amount of time before or after a first date, use the following: $datestr = "Jan 30 1999 13:00 EST"; $deltastr = "12 hours ago"; $deltastr = "in 3 business days"; =over 4 =item B $date = new Date::Manip::Date; $delta = $date->new_delta(); $date->parse($datestr); $delta->parse($deltastr); $d = $date->calc($delta); =item B $date = DateCalc($datestr,$deltastr); =back If the delta is a business delta, it will do a business mode calculation. The L manual has information about these, and other types of calculations. =head1 COMPARE TWO DATES To take two different dates and see which is earlier, do the following: $datestr1 = "Jan 30 1999 13:00 EST"; $datestr2 = "2/Mar/1999 15:30:00 +0500"; =over 4 =item B $date1 = new Date::Manip::Date; $date2 = $date1->new_date; $date1->parse($datestr1); $date2->parse($datestr2); $date1->cmp($date2); => -1, 0, 1 =item B $date1 = ParseDate($datestr1); $date2 = ParseDate($datestr2); Date_Cmp($date1,$date2); => -1, 0, 1 =back =head1 TO EXTRACT INFORMATION ABOUT A DATE OR DELTA If you have a date or a delta, you can extract information about them as follows: $datestr = "1:24:08 PM EST Feb 3, 1996"; $deltastr = "12 hours ago"; =over 4 =item B $date = new Date::Manip::Date; $delta = $date->new_delta(); $date->parse($datestr); $delta->parse($deltastr); $str = $date->printf("It is now %T on %b %e, %Y."); => "It is now 13:24:08 on Feb 3, 1996." $str = $delta->printf("In %hv hours, %mv minutes, %sv seconds"); => "In -12 hours, 0 minutes, 0 seconds"; =item B $str = UnixDate($datestr,"It is now %T on %b %e, %Y."); => "It is now 13:24:08 on Feb 3, 1996." $str = Delta_Format($deltastr,"In %hv hours, %mv minutes, %sv seconds"); => "In -12 hours, 0 minutes, 0 seconds"; =back The L manual contains all of the format codes that can be used to extract information from a date. The L manual contains the codes for a delta. =head1 WORKING WITH EPOCH Date::Manip can easily be used to work with the number of seconds since the epoch (Jan 1, 1970 00:00:00 UTC). If you have a date, and you want to find out how many seconds it is after the epoch, you can do it in the following ways: $datestr = "1999-04-30-15:30:00 EDT"; $secs = 1234567; =over 4 =item B To find out how many seconds have elapsed on a certain date, you can do the following: $date = new Date::Manip::Date; $err = $date->parse($datestr); $str = $date->printf('%s'); => number of seconds To find out the date that is a certain number of seconds since the epoch, you can use the following: $date = new Date::Manip::Date; $err = $date->parse("epoch $secs"); C<$date> now contains the date wanted (in the local time zone) =item B To find out how many seconds have elapsed: $str = UnixDate($datestr,'%s'); => number of seconds To find the date that is a number of seconds since the epoch: $date = ParseDateString("epoch $secs"); =back Note that Date::Manip will work with both positive seconds (for dates that have come since the epoch) and negative seconds (for dates that occurred before the epoch). =head1 RECURRING EVENTS To find a list of dates where a recurring event happens (even very complex recurrences), do the following: =over 4 =item B # To find the 2nd Tuesday of every month from Jan 1 1999 to Apr 30 1999 $recur = new Date::Manip::Recur; $start = $recur->new_date(); $end = $recur->new_date(); $start->parse("Jan 1 1999"); $end->parse("Apr 30 1999"); $recur->parse("0:1*2:2:0:0:0",$start,$end); @date = $recur->dates(); # To find the Monday after Easter in 1997-1999 $recur = new Date::Manip::Recur; $recur->parse("*1997-1999:0:0:0:0:0:0*EASTER,ND1"); @date = $recur->dates(); =item B # To find the 2nd Tuesday of every month from Jan 1 1999 to Apr 30 1999 @date = ParseRecur("0:1*2:2:0:0:0","","Jan 1 1999","Apr 30 1999"); # To find the Monday after Easter in 1997-1999. @date = ParseRecur("*1997-1999:0:0:0:0:0:0*EASTER,ND1"); =back The L manual contains information about recurring events. =head1 WORKING WITH DATES IN ANOTHER LANGUAGE If you want to work with dates in a language other than English (but you are only working with a single language), do the following: =over 4 =item B $date = new Date::Manip::Date; $date->config("Language","French","DateFormat","non-US"); $date->parse("1er decembre 1990"); =item B Date_Init("Language=French","DateFormat=non-US"); $date = ParseDate("1er decembre 1990"); =back The L manual has a list of all supported languages (in the section on the Language config variable). The meaning of the DateFormat config variable is also included. =head1 WORKING WITH TWO DIFFERENT LANGUAGES If you want to work with dates in two (or more) languages, it is STRONGLY recommended that you use the OO interface. The functional interface will be much slower since it has to re-initialize a lot of language-specific stuff every time you switch back and forth between languages. =over 4 =item B $date_eng = new Date::Manip::Date; $date_eng->config("Language","English","DateFormat","US"); $date_fre = new Date::Manip::Date; $date_fre->config("Language","French","DateFormat","non-US"); Use the C<$date_eng> object to do English operations, the C<$date_fre> object to do French operations. =item B If you are working with both French and English dates, you can call the following to switch between them: Date_Init("Language=French","DateFormat=non-US"); Date_Init("Language=English","DateFormat=US"); This is NOT recommended. Use the OO method instead. =back =head1 BUGS AND QUESTIONS Please refer to the L documentation for information on submitting bug reports or questions to the author. =head1 SEE ALSO L - main module documentation =head1 LICENSE This script is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =head1 AUTHOR Sullivan Beck (sbeck@cpan.org) =cut