Hello,
Do you mean Time Zone (/etc/localtime)? If so, and it really changed then Directadmin by itself has nothing to do with that. I'd rather say it's either your VPS issue (if is used any), or software upgrade related.
im set time by this command :
# ntpdate 0.asia.pool.ntp.org
And what is wrong with that? Now I'm not sure I get what troubles you.