What is easiest and effective way to fetch data based on time Zone.

i have more than 50 tables in Database and storing Action Date (Created On/Modified On) in UCT+00

for filtering data from different tables based on Created Date / Modified data as per local time i am adding/subtracting hours to the Created/Modified date using DATE_ADD function which is serving purpose.

I am looking for something generic where i can set/pass client timezone and filter data