This is the 11911th most frequent Turkish word.
geçirmişse
"If he/she/it has experienced/undergone."
The word 'geçirmişse' here is used to indicate the conditional possibility of having experienced a difficult time.
Eğer sınavdan düşük not almışsa, zor bir dönem geçirmişse suçlamamalıyız.
If they have scored low on the exam, if they have gone through a difficult period, we shouldn't blame them.
In this sentence, 'geçirmişse' suggests the situation of potentially having had a pleasant day.
O bu sabah köpeğiyle uzun bir yürüyüşe çıkmışsa, harika bir gün geçirmişse ne güzel.
If he has gone on a long walk with his dog this morning, if he's had a great day, how wonderful.
Here, 'geçirmişse' denotes the conditional likelihood of having had enjoyable times during vacation.