In Minecraft PS4, Does 'Passing the Time' trophy have to be done in 1 session or over multiple sessions?

Multiple.

"This trophy requires you to play for 100 in-game days, each is a full 20 minutes, being equivalent to 33 hours play time, this will likely be the last trophy you obtain. Unfortunately there's no way to speed this up or manipulate the trophy so you must allow the full 100 days pass for it to unlock normally. "

It has to be in a single world, single game, and from the looks of all the informayion I can find, a single session.
All the advice seems to be to set the game to Peaceful, and leave it idle for a while.

No soon as.

However you want to break it up. All at once, a day at a time, whatever. It allegedly has to be 100 hours in the same world, but not 100 in-game days all in one session.

I've gotten the trophy (and achievement) an hour or so into a game session, but it was on a world that I'd played with a lot over time.

It doesn't have to be in one session thats for sure