By calling six flags or visiting their website or downloading the app. Certainly not by asking here.
Download appš
The Six Flags App is the most useful tool to figuring out at what times they will close each day and also on the rewards section of the app it will let you know which days you can bring a friend for free with usually are Mondays - Thursdays
Closing times vary by weather it's best to download the app for up to date notifications.
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