EpochLab

Day of Week Calculator

What day of the week is any date?

The weekday for any date, past or future, plus its week number, day of the year, and which weekday that date falls on in the surrounding years.

Questions people ask

The things that come up about day of week calculators, answered plainly.

Does this work for historical dates?

It works in the proleptic Gregorian calendar — the modern one extended backwards. Before a country adopted it, the historical weekday differed: Britain and its colonies skipped 3 to 13 September 1752, and Catholic Europe skipped 5 to 14 October 1582.

Why does the same date move by one weekday each year?

Because 365 divides by 7 with a remainder of 1. A leap year has a remainder of 2, which is why the shift is sometimes two days.

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