My advice would be to keep epoch time in your database for the benefit of all the apps you might use in the future, its just much more wisely used than DATETIME, theres a good article about these issues in more depth here, (look specifically at the Obtaining Epoch time section)[1]
when you extract your epoch time from your mySQL database, if you want it in a DATETIME format use the query:
SELECT FROM_UNIXTIME(myEpochDateC
ol) FROM mydb.myDateTable; in your C# instead of
SELECT myEpochDateCol FROM mydb.myDateTable;
[1]
http://billauer.co.il/blog/2009/03/mysql-datetime-epoch-unix-time/