I too am experiencing this. This is not a new "slowness", but rather something that has existed for me from the beginning of using Proton calendar... Very annoying. Very slow to load every time I switch to another day.

I use Proton Calendar on iOS with the latest iPhone and creating or updating an event takes 10s. Deleting takes 5s. My partner is on a slower android phone and it’s similar. This is a major UX issue especially when you want to create multiple events after each other. This is the main reason my partner switched back to Google Calendar and I’m considering the same although I pay for Proton Business Suite.

So I gueass I'm not the only one. Proton calendar has ben extremely slow to load recently, taking much longer than previously. (Android.) It now routinely takes 15-20 seconds to load. The same amount of delay also occurs when changing months or layout (day/3d/week/month).

Please fix it!!

It is so slow that I sometimes think to remove it and not use it. I pay for Proton DUO and calendar is really f**g slow. Sorry but it takes 15-20sek to save it. (iPhone 13Pro here). Besides, no drag and drop. Each change require popup and save again.

Having this same problem on iPhone. I’m a fast paced person and the app just isn’t cutting it. The calendar takes way too long to load.

I've noticed the more shared calendars I have, the worse it gets, at a drastic rate. Then moving forward a week, and I have to wait another 10-15 seconds. If I need to move forward a few weeks, I will likely forget what I was looking for.

I have read that it takes a lot of time to decrypt everything... but surely there is a better way. Like, encrypt smaller chunks of time, so that only the currently-viewed month needs to be decrypted, or something. Maybe the server can bundle shared calendars together so the group can be decrypted (instead of what it seems like now, each one is opened, one at a time).

Or, give guidance to users, like: you have 15 years of history on this calendar, you'd have a better time if you moved the first 14 years into a separate calendar that you don't have enabled most of the time, or something. (And then make it easy to archive old events).

Same for me, takes 5-10 seconds every time. Sometimes even when I just had it opened.
Could this be related to me using shared calendars? But I need those.