I wasn't sure if this should be classed as Software or Research, but it may be both. I know sometimes it can be tricky to get the right day of the week for a specific date either years in the past or in the future. For this purpose (and for my religious practices) I have developed a calendar program which can accurately predict the dates of the Gregorian calendar from 1582 until 3999. Additionally it can also predict the dates of various Roman Catholic feasts and solemnities, though the rules governing the dates of celebrations such as Easter could change in future - the program assumes the dates based on current rules. Hopefully this calendar will be of use to anyone wanting to research past dates or predict future dates. The calendar uses the list of feasts and solemnities in the UK - other countries and denominations may have other lists and rules, but this should still be fairly accurate. To view the dynamic calendar, please visit http://rcchurch.co.uk/vatical.htm I hope it will be useful regardless of your religious beliefs. I promise I won't try to convert anyone