why Unix Time Stamp for same time is different in different timezone

Question

Why 7/18/2013 11:33 is different in GMT timezone and in my local Time Zone (Asia/kolkata)? As Unix time-stamp are the ticks being calculated since epoch time 1/1/1970 00:00:00 GMT so i know that there the epoch time had occurred at different interval in different timezone but still. the number of second elapsed should have been same

For example if I(+5:30 GMT) and My friend(+5:00 GMT) starts counting the ticks from 00:00 Hrs respectively so at 18:00 Hrs in both timezone number of ticks should be same. So why same thing is not true with the Unix time-stamp.

Need to Understand the concept fully.

Answer 1

For example if I(+5:30 GMT) and My friend(+5:00 GMT) starts counting the ticks from 00:00 Hrs respectively so at 18:00 Hrs in both timezone number of ticks should be same.

No, because both of you start counting from 00:00 UTC. That's the definition. So for you, that will mean the number of ticks since 18:30, and for your friend it will mean the number of ticks since 19:00.

The idea is that a single instant in time has the same timestamp value everywhere. So if I were calling you now (and ignoring phone delays) we could both agree that "now" is a Unix timestamp of 1374130418. You may have a different local time to me, but we can express "now" in a common format.

See the "core concepts" part of the Noda Time user guide for more discussion of local time vs "global" time.