Liturgical Calculator
You can click on the buttons at the bottom, or click in the text box at the top and type in any date from 1583 to 4099 (then press the Enter key).
The results match my missal for the years 1974 to 1999 - after that please double check with other sources (see the disclaimer on Ronald Mallen’s web page).
From Advent 2006 there are changes to the dates for Ascension and Corpus Christi in England and Wales. I hope to add the necessary correction soon.
If nothing useful appears above, you may not have Java installed on your computer. You can read about Java and download it, if you wish, from the Java web site.