Batch bulk delete google calendar

 https://www.youtube.com/watch?v=hJdGBmHDafA

In short:

1. Select calendar, say NFL2025-26, 設定與共用->匯出日曆, say. kpchiaoo@gmail.com.ical.zip
2. Unzip kpchiaoo@gmail.com.ical.zip, and get NFL2025-xxxx.ics
3. Edit NFL2025-xxxx.ics, Replace all
   "STATUS:CONFIRMED"
   to
   "STATUS:CANCELLED"
4. Save it as NFL2025-xxxx-calcelled.ics
5. Then import NFL2025-xxxx-calcelled.ics back to google calendar, NFL2025-26
6. Done