There is usually no time limit for special exhibits. Also, the ticket you buy at the museum is also good for entry at The Palace For The Legion Of Honor on the same day.
The time is for when you can enter the Gauguin exhibit. They limit the amount of people per time slot, that's all. You can go to the rest of the museum all day if you'd like
Great question. I don't know the answer. The person who sold us our ticket to the main gallery, not special exhibit, said we had the rest of the day. No time limit. I'd call because the staff is very helpful.
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