Liturgical Data
My Sunday Missal has a table of 'movable feasts'. It tells me useful things such as the dates of Ash Wednesday, Easter, Pentecost, etc, the Sunday and Weekday Cycles and what 'week' it is when we start again after Pentecost.
Unfortunately my missal only reaches 1999 - a low-tech Y2K problem - so I started to look up ways of calculating these dates. I found a very good web-page on the date of Easter provided by Ronald W Mallen of the Australian Astronomical Society.
I have used his method in a simple Liturgical Calculator. You can try it out if your browser is 'Java-enabled'. It will probably take a few seconds to get going.