Say I have the users' preferred date time format in a POSIX format string. It's easy to display the local time in a format that they like: 
use POSIX;
my $format = '%d-%m-%Y %H:%M:%S';
print POSIX::strftime($format, localtime());

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However, how do I go the other way? Say I want to record all time in epoch seconds. I know the users' preferred POSIX date formats, so how do I take any format and convert it?

In reply to Converting POSIX format date/times to epoch seconds by Anonymous Monk

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