[supercat]

According to Jimmy Akins, who is a great one for good solid answers, and from whom I lifted this info, it refers to a 24 hour period.

So when the period from local midnight to local midnight is 24 hours, that's a "day". Got it. What happens if the period from local midnight to local midnight is something other than 24 hours?

[Knitting A Conundrum]

I suspect it's more your 24 hours. You receive Eucharist at 8 in the morning, then again 12 hours later, then you better wait a full 12 hours your personal time before receiving again, no matter how many time zones you cross! Or that's how I would feel obliged to interpret it for my personal doings.