Why does the OLE variant date format use 30 December 1899 as its zero point?

Raymond Chen

In 2006, via the suggestion box, Chris J asks why the OLE variant date format has such a strange zero point. Its zero point is 30 December 1899, as opposed to 1 January 1900 (SQL Server’s zero point) or 1 January 1970 (the unix zero point).

It turns out I don’t have to answer this because Eric Lippert explained it three years before the question was posted, and then some time later posted a puzzle regarding date calculations.

Public Service Announcement: This weekend marks the start of Daylight Saving Time in most of the United States.


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