I may well have missed this by not reading absolutely everything available on the ProZ site (there's an awfull lot!),
No need to do that - you can use the Search function on the left.
but how does ProZ handle timezones. I mean the timestamp that appears next to a job posting or Kudoz posting - is it according to the time zone of the submitter, or is it ProZ's own time zone (whichever of the American time zones that might be)?
Actually, this is answered in the FAQ
HTH - Ralf