Need to dig out the notes on just how a TIMESTAMP works in Firebird. It is essentially two 32 bit numbers, one being the date and the other time as a fraction of a day. The date element runs from January 1,100 AD to February 28, 32768 AD. For reasons which will not be explained now, the '0' date is November 17, 1898 and caclulations on date ranges prior to that are done with -ve numbers

http://www.firebirdsql.org/en/firebird-date-literals/ for the conversion to convential date formats ...

The time element was originally only returning seconds, but later developments provided the option for millisecond accuracy.

Some more historic material will be added later.