ٱقْتَرَبَتِ ٱلسَّاعَةُ وَٱنشَقَّ ٱلْقَمَرُ
Iqtarabatis Saa'atu wsan shaqqal qamar
The Hour draws near; the moon is split in two.
The hour has drawn near, and the moon has split.
Both verbs stand in the perfect tense, so the surah opens with two things spoken of as accomplished, and everything after it reads as consequence. The tradition has taken the splitting of the moon two ways: as a sign given at Mecca during the Prophet's lifetime, and as an event of the hour itself, put in the completed tense because it is certain. Which reading you hold changes what the next verse's dismissal is answering.