Fast calendar and business date calculationshttp://search.cpan.org/perldoc?Date::Business
Date::Business provides the functionality to perform simple date manipulations
quickly. Support for calendar date and business date math is provided.
Business dates are weekdays only. Adding 1 to a weekend returns Monday,
subtracting 1 returns Friday.
The difference in business days between Friday and the following Monday (using
the diffb function) is one business day. The number of business days between
Friday and the following Monday (using the betweenb function) is zero.