Not sure how this happens, but here is what I discovered:
For some unknown reason, an event was with a start date in 1901. Thus, the module “calendar_new” has a ton of calculations, which makes it time out. The module should be smarter, I agree.
Workaround is to remove calendar_new module:
This could also affect other calendar modules so remove them as well. Please note that you can easily re-instate via the admin panel after, as it is not deleted but just unassigned.
Now, any theories on the 1901? User error? bug?