How does the CDC define an overnight stay?

I read this quote from the CDC reported by jcaron:

If I have one or more connecting flights to the US, does the 3-day period apply to the first flight or the last one? Do I need to get another test if I have a connecting flight?

If your itinerary has you arriving to the US via one or more connecting flights, your test can be taken within the 3 days before the departure of the first flight.

If the 3-day testing period expires before one of your connecting flights, you only need to get retested before boarding connecting flights if:

You planned an itinerary incorporating one or more overnight stays en route to the US. (NOTE: You do not need to be retested if the itinerary requires an overnight connection because of limitations in flight availability.), OR

The connecting flight is delayed past the 3-day limit of testing due to a situation outside of your control (e.g., delays because of severe weather or aircraft mechanical problem), and that delay is more than 48 hours past the 3-day limit for testing.

E.g. any stay longer than x hours and including midnight? If the stay is between x AM and y AM, which set of {(x, y), x<y} turns it into an overnight stay? etc.

I don't mean to be overly scrupulous but a friend of mine is flying to see me in the US and his flight has a layover between 5 and 8 hours from very early AM (quite close to midnight) to the beginning of the morning, and I genuinely have no clue whether the CDC defines it as an overnight stay.

Best Answer

There are two things:

You need to be retested if you planned an itinerary incorporating one or more overnight stays en route to the US. But..
You do not need to be retested if the itinerary requires an overnight connection because of limitations in flight availability.

In other words, if you are taking the first available flight at each of your connections then you don't need to be retested, regardless of whether the stay is "overnight" or not. If this applies to your friend they do not need to be retested.