Universalcalendartitle The Universal Calendar offers the following functionality: find the weekday for any date calculate a date based on a given date an a number of days difference calculate the number of days between two dates calculate the week of the year for a given date calculate the start and end date for a given week show the public holidays for a year (year 0 - 9999) The calendar can hide itself in the system tray. It's week of the year functions make it usefull also for business use.