Yes, sorry I forgot to mention it. I have already tried changing to "system default", "Asia/Kolkata" (my timezone), but the issue continues to haunt me.
After a bit of tweaking, the below setup show me India time, but as you can see, its a wrong setup.
Admin Login > Settings > timezone = UTC
Agent Login > Preferences > timezone = Europe/Athens
Note: I have 2 separate installations of OSTicket on the same server & I have set up both of them as above