Date calculation usage in different Unix environments

From: http://blog.rootshell.be/2006/05/04/solaris-yesterday-date/

Solaris & yesterday date?

The GNU version of date (1) has a nice flag-Date. It's very easy to format dates in the past or future:

$ Date + % d-% m-% Y04-05-2006 $ date -- date yesterday + % d-% m-% Y03-05-2006 $ date -- date "-6 months" + % d-% m -% Y04-11-2005

The Solaris version of date (1) has no such nice flags. So, how to print another date?

Direct in a shell:

$ YESTERDAY = 'tz = GMT + 24 date + % d-% m-% y '; echo $ YESTERDAY03-05-2006 $ YESTERDAY = 'tz = GMT-48 date + % d-% m-% y'; echo $ YESTERDAY06-05-2006

But, in this case, we are limited to a few days in the past or future. Another solution is Perl:

$ Perl-e 'use POSIX qw (strftime); print strftime "% a % B % e % H: % M: % S % Y",/localtime (time () -3600*24*2); 'tue May 2 14:59:41 2006