Massive discrepencies in timetable info Piran->Ljubljana

Just a guess, but I suspect the online version is more up to date. They may not have gotten around to all the bus stops to change the posted schedule. We had that happen in San Francisco recently.

Usually asking a local hotel desk can get you the scoop on the bus schedule—especially for a route as popular as Piran to Ljubljana.

I've found schedules posted at the bus station from which the bus is to depart (not at a random bus stop) to be accurate, but it does make one nervous when there's inconsistent information floating around. In 2015 the fellow selling tickets at the Ljubljana bus station handled English very well, and the staff at the tourist office were very helpful, so those are two potential sources of clarity.

I will say that elsewhere in the Balkans, when I asked a local tourist office a question about bus schedules they couldn't immediately answer, they picked up a phone and called the bus station in the departure city rather than looking online. Seeing that happen repeatedly made me reluctant to rely on bus schedules found online.

You take one bus from Piran to Koper (the train/bus station).
Then, you take a bus or train to Ljubljana. The train is slow, but more scenic. I enjoyed it.