Hi!
I think we need to where you live in order to tell the time difference.... and is Sereban a place in Singapore?
But lets say that you live in India and that we know that India is 2:30 hours behind Singapore.
So if we leave at 21.30 from India-time and arrive at 02.25 Singapore-time we must first determine what 02.25 in Singapore time is in India time.
02.25 in Singapore is 02.25-2.30h=>23.55 in India time.
Hence, we started travelling on 21.30 and reached our destination on 23.55. The travelling time is 23.55-21.30= 2 hours and 25 minutes
This asuming that you are living in India :)
I hope this helped you.