Why can I store dates earlier than 1753 using the datetime datatype?
This was done for historical reasons, and started with the original Sybase specification for the datetime datatype. In what we sometimes refer to as the western world, we have had two calendars in modern time: the Julian and the Gregorian calendars. These calendars were a number of days apart (depending on which century you look at), so when a culture that used the Julian calendar moved to the Gregorian calendar, they dropped between 10 to 13 days from the calendar. Great Britain made this shift in 1752, and in that year, September 2nd was followed by September 14th. Sybase decided not to stored dates earlier than 1753 because the date arithmetic functions would be ambiguous. However, other countries made the change at other times, and in Turkey the calendar was not shifted until 1927. The new date and datetime2 times in SQL Server 2008 do allow us to store dates back to 0001-01-01. For one of the best articles on the web about datetime issues in SQL Server, see Tibor Karaszi’s website
