It is celebrated on 21 March every year, a date originally determined by astronomical calculations.

UNESCO: Culture

No servicer has a data repository with automated processing rules designed to keep files and calculations up to date with the constant changes.

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When that day came and went, Weinland amended his calculations, claiming an error and revising the date to May 27, 2012.

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Most older software systems were written with two-digit date fields that are expected to read the "00" in 2000 as "1900" and consequently make incorrect calculations.

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