I am experiencing similar issues to the post on 12/19. Dates became scrambled after installing 4.4.20. Rolled back to 4.4.19 and dates went back to normal. However, all recurring events broke and went to page not found even though they were visible in the pop up. I rolled back The Events Calendar and then reinstalled version 4.6.8. Everything now works.
Currently our staging site is down, so I am not able to troubleshoot by turning off plugins and changing themes.
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Reporting the same issue as: https://theeventscalendar.com/support/forums/topic/the-events-calender-pro-4-4-20/