72 hours or 3 Days for Antigen for US

[Lori Williamson]

Guys, can you confirm if it is 72 hours or 3 days for the antigen results? Westjet says 72 hours:

COVID test requirements
Every guest two years of age and older is required to have either:

• A negative COVID-19 test taken within 72 hours of scheduled departure
• COVID-19 PCR, NAAT (i.e. RT-LAMP) or Rapid Antigen tests are accepted.

However, this is what I see on the CDC Website:

Why does the Order specify 3 days rather than 72 hours? What is considered 3 days?
The 3-day period is the 3 days before the flight’s departure. The Order uses a 3-day timeframe instead of 72 hours to provide more flexibility to the traveler. By using a 3-day window, test validity does not depend on the time of the flight or the time of day that the test was administered.

For example, if a passenger’s flight is at 1pm on a Friday, the passenger could board with a negative test that was taken any time on the prior Tuesday or after.

I am trying to figure out when to book our tests, but my daughter works late and I need to do it before the hotel cancellation time, just in case.

 

[damo]

It is 3 calendar days going from Canada to US and 72 hours going from the US to Canada.

 

[KristaZ]

3 calendar days for back to the US. When I returned in August my test was something like 78 hours old. Didn't matter because it was still 3 calendar days.