Last year I had to perform date arithmetic in C shell scripts on a locked down server (no way to install or compile programs and obsolete or missing utilities).

Last year I had to perform date arithmetic in C shell scripts on a locked down server (no way to install or compile programs and obsolete or missing utilities). I considered Perl, since it was the only scripting language interpreter, but the good enough (on paper) date handling libraries I found on CPAN turned out to require a far newer Perl 5 version that was available. I'm afraid that the best-case Perl solution would have been more difficult to write than the roundabout but reliable and easy to understand final solution (Oracle SQL functions executed through the command-line SQL*Plus client).