Would timestamp validation fail when servers and clients running in different timezones?

No. WSS4J keeps the time as UTC - so different timezones shouldn't matter.

Even in different timezones - if you have the correct time corresponding to that time zone - then it should be fine.

For example :

Time Zone A [GMT + 8] : Correct Time Now : 4.00 AM

Time Zone B [GMT + 11] : Correct Time Now : 7.00 AM

Then it should work with no issues.

But in the same case if you have the time, incorrectly, in Time Zone A as 5.00 AM [ in a case where it should be ideally 4 .00 AM] - then timestamp validation will fail.

So - timezone wouldn't be an issue if we still have the correct time in each case corresponding to the timezone - it belongs to.