I do not know, if I understood your question right, but Timestamp is not the time, it gives you the exact time (and date) between 1901 and 2038.
Anyway I personally prefer to store this information in a datetime field and convert it to a timestamp if I need one, because this way the information in your database is easy readable and can be handled better by databases that do not support timestamps. But of course the timestamp has some advantages, too.
Grisu