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Question

What are the century anchor days you need to memorise?

Answer

A doomsday for each century's "00" year: 1800s → Friday, 1900s → Wednesday, 2000s → Tuesday, 2100s → Sunday.

Century Anchor #
1700s / 2100s Sunday 0
1800s / 2200s Friday 5
1900s / 2300s Wednesday 3
2000s / 1600s Tuesday 2

The pattern repeats every 400 years (the Gregorian leap-year cycle), so 1700s and 2100s share Sunday, and so on. For most everyday dates you only need the middle rows: Wednesday for the 1900s and Tuesday for the 2000s.

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