Originally Posted by Ditto

Technically speaking the gazette doesn't specify either, but of course you also have no control on when the swab is actually processed, so best would be to test within 72 hours.
I'm not sure a swab collected Friday evening would be much different to one collected Saturday morning.

Having had to look at the gazette again I also realized it is saying "Polymerase Chain Reaction ( "PCR ") test certificate or a valid COVID -19 negative test certificate" which would actually suggest other types of tests should also be allowed, however in all press releases/briefings a PCR test was mentioned to be required.

I would say at the end of the day it's all about risk management, if you get a PCR swab done in <72hrs to your flight, you are guaranteed to have no issues, anything else and you risk not allowed to board your flight due to how an airline (employee) interprets the regulations.