MySQL. How to get UTC timestamp from datetime column?

Question

MySQL

1. The timezone on the server is set to GMT-7 and there is no way to change it.
   
2. I have a DateTime column that contains "2016-03-03"
   
3. You need to get a timestamp, assuming that the column contains the time in UTC.
   

UNIX_TIMESTAMP returns 1456963200 instead of 1456988400 (difference 25200 = 7 hours).
How to decide?

Answer 1

UNIX_TIMESTAMP(DateTime)+7*3600

Answer 2

UNIX_TIMESTAMP(CONVERT_TZ())
and any