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I did something similar recently with my daughter's school calendar and ChatGPT with gpt-4o; her school has a ton of closures/teacher work days, I fed the PDF of the calendar in and asked it for all the dates that impacted 2nd grade, then asked it to create an icalendar file for them.

Oddly, it didn't want to create the actual file, but gave me a Python script for doing so; you just need to be sure to tell it what time zone you are working in and that you want it to be an all-day event, or you'll get suboptimal results.