Reset the clock/timer properly. Find the manual (should be easily available online if you can't find the paper one) and read it.
Manual here. Probably similar o the oven you have:
http://www.manualslib.com/manual/202147/Samsung-Bf641fst.html#manual
Note on page 6 it says:
Time setting
If the oven is plugged to the power supply for the first time, its display will illuminate for short time and after 3 seconds 12:00 starts to blink. *****Before the oven can be used the time setting must be completed*****.
Anon, September 2016