The Date Calculator is a date utility for genealogists. You can enter any date and convert it between Gregorian, Julian, Hebrew, and French Republic calendars and find its day of the week. You can enter two dates and find the time span between them. You can do various other date and time calculations and conversions such as adding time to a date, subtracting time from a date, or adding and subtracting times.

A unique feature of the Date Calculator versus other date utilities is that you can enter fuzzy dates, such as just a month and year (APR 1901), just a year (1864), or a range of dates (FROM 1845 to 1867), and still do useful calculations. The calculations will give all possible answers for the date and time information provided. Being able to do calculations with imprecise dates and time spans is a very useful tool in genealogy research.