Originally Posted by
dwugson
There should be some consensus with the 72 hour limit to allow for the time change between countries.
I hope this doesn't come across rude but I don't really understand your issue with time zones. 72 hours is 72 hours. If you cross a time zone, that doesn't affect how long you have lived for. The SA rule is 72 hours from time of departure (on one through-ticket so allowing for a transit), so that is 72 hours in the time zone of the departing airport.
If you want to layover somewhere that needs a test within ## hours of arrival, then you could use google to ask what time the aircraft arrival time in that country is where you are now, then count back the appropriate number of hours. Or you may find it more intuitive to convert the time of arrival at the arrival airport to UTC (formerly Greenwich Mean Time), taken ## hours back and then convert that to your time zone as the earliest time you could take the test?