Find Earliest Possible Post

What is the earliest possible date for a post? 1 January 1900 is good enough for what I have in mind. (P.S. Today is really 11 May 2009.)

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Later: Entering '1/1/1900' is saved as '1/1/00', meaning '1/1/2000'. Is that the earliest possible date?

Now I'll try '1/1/1920'.

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Later: That also defaults to '1/1/00'. Ditto for '2/2/1920'.