# getting yesterday's date
use Date::Calc qw(Today_and_Now Today Add_Delta_YMD Add_Delta_DHMS);
# use Date::Calc to subtract one day from today's date
my ($year, $month, $day, $hours, $minutes, $seconds) = Add_Delta_DHMS(
+Today_and_Now(),-1,0,0,0);

# get date of last month by subtracting a month
my ($year2, $month2, $day2) = Add_Delta_YMD(Today(),0,-1,0);
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my $yesterday = time() - (24 * 60 * 60);
my ($day, $month, $year) = localtime($yesterday)[3,4,5];
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However, yesterday's date may not be twenty-four hours ago. The day on which daylight savings time (DST) ends is 25 hours long; the day on which DST begins is only 23 hours long.

Thus if you calculated the date 24 hours earlier during the last hour of the day DST ended you would get an erroneous result using the above formula, i.e., "yesterday's" and today's dates would be the same.

Similarly if you calculated the date 24 hours earlier during the first hour of the first whole day after DST began you would also get an erroneous result using the above formula: "yesterday's" date would be two days before today's date.

'perldoc perlfaq4' has a workaround by Russ Allbery that fixes the DST problem.

Update: Corrected above to state that the formula at top would provide incorrect results in the last hour of the day DST ended, not the first hour of the day after it ended.

Similar problem came up recently with a bbs running on a server in the U.S. for a Japanese audience. Daylight savings time and so on were involved. As long as you stick to unix time (seconds from epoch) you can calculate things like "24 hours ago" easily. Staying in Greenwich time until the end is useful.

But if you want to do lots of other calculations (like I did for a recent timesheet tracking program that prints a calendar on top of a form) Date::Manip can do just about anything. Careful, it and CGI are some of the biggest modules in Perldom. (My process was 9 mb).

Here you are. You are fairly non specific about what consitutes "last month" so I have just used 30 days.

cheers

tachyon

$time = time();
print "Yesterday (24 hours ago): ".localtime($time-24*60*60),"\n";
print "Last month (30 days ago): ".localtime($time-30*24*60*60),"\n";
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my @date = localtime(time);
#get yesterdays date;
$date[3]--;
$date[6]--;
my $run_date=strftime("%A %e %B %Y", @date);
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my @date = localtime(time);
#get last months date;
$date[4]--;
my $run_date=strftime("%A %e %B %Y", @date);
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Sunday 27 May 2001

Diarmuid

ParseDate can take an 'english like' string and then output that date in its own format of YYYYMMDDHH:MM:SS

UnixDate is another function that converts ParseDate's output to a customisable format, similar to localtime as shown above, it lets you output things in a more customisable format if that is of any concern.

use Date::Manip qw(ParseDate UnixDate);

#examples giving epoch seconds
$date = ParseDate("last month");
$date = ParseDate("yesterday");
$date = ParseDate("250 days ago");
$date = ParseDate("2nd tuesday in april");

#date formating example
$date = UnixDate($date, "%d-%m-%Y");
...
...
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Indeed, Date::Manip's ParseDate allows for a lot of flexibility. Here is an example of how I used ParseDate to create a very handy "sleep until" script.

This is subroutine written by me which I use to get yesterdays date

1.i

# get yesterdays date
my $date = &plsub_getdate(1);


## *** Get date number                                     *** ##
## parameters - dday (optional)                                ##
## dday       - difference day         - $_[0]                 ##
## frmt       - Date Format            - $_[1] {WIP}           ##

sub getdatenum
{
  use POSIX qw(strftime);

  if ($_[0])
  {
    $date = strftime "%Y%m%d", gmtime(time - (86400 * $_[0]));
  }
  else
  {
    $date = strftime "%Y%m%d", gmtime;
  }

  return $date;
}
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Now I suppose you will work to get 2.i. If still you have any problem mail me joel_divekar@yahoo.com

Jamnet