[ This is bug affects only to people using the spamassassin spam filtering software ]
Fabian Arrotin reports about this spamassassin bug, which tags mails dated 2010 and later - as potential spam (increases its spam-score). This is not silly - many spammers use fictional (far past/future) dates, wishing their spam would stay in the top/bottom of the long list of mails.
This bug alone didn't cause false positives in my spam folder (only increased the score from 0.0 to 0.6), but in some configurations or situations it could happen.
The Fix