crontab inconsistent with the system time

After migrating online database to the virtual machine, operation and maintenance is not the time to modify.

In the latter part of the time is modified, on the database should also be amended to modify, but the backup time is not timed tasks performed at 4:00, but performs at noon 12:10 minutes.

The reason is that after the modification time, need to restart the crontab

Modify the database time

set time_zone = '+08:00';

set global time_zone = '+08:00';

flush privielges;

Restart crontab
/etc/init.d/crond restart