Limit the number of event on the ics file to 1000

[edgarcosta]

This is another thing to note, specific to Google Calendar: https://support.google.com/calendar/thread/725096?hl=en&msgid=10889694

Google says the limit is 1MB (https://support.google.com/calendar/answer/45654?hl=en)... I usually split into 1.8MB files without problems, but according to this post the actual limit is 1,111 events: https://support.google.com/calendar/thread/1723215?hl=en

My current ICS file downloaded from researchseminars.org is 2.1MB. Directly using my link https://calendar.google.com/calendar/render?cid=http%3A%2F%2Fresearchseminars.org%2Fuser%2Fics%2FIjI0NSI.LjXVFmFMHiF502lVmYYHn4qsSOw to create a new calendar in Google will result in the loss of many events. For example, 12 out of 58 events today will be lost, and 9 out of 34 tomorrow will be lost. Importing the downloaded ICS file to Google works fine (apparently all events show up). I notice that all earlier events (prior to today) also seem to be present in the ICS file. Probably they are also are present when Google tries to sync with the link. Can you reduce the size by removing earlier events, say more than one week ago? And if necessary, only sync events within one week from today? In my use case, the calendar synced from researchseminars.org is merely for tracking things, and I'll manually copy those seminars I am interested in and actually plan to attend to my main calendar every night, so syncing 1-2 days each time would be sufficient to me.

Thanks for your attention!

Addendum: I also find that probably due to this oversize issue, the updated time, title, and abstract of some events on researchseminars would not update in Google Calendar, even after you refresh.

Originally posted by @alreadydone in https://github.com/roed314/seminars/issues/39#issuecomment-649897038

[poonen]

Given what @alreadydone reports, maybe on the Account page, near "Export favorites to..." one could add two checkboxes saying something like [x] Do not sync past events more than one week old. [ ] Do not sync events more than one month in the future.

with the first being checked by default, and the second unchecked by default. (I suggest one month in the future rather than one week since I think that most people will want to see upcoming talks that are more than one week in the future.)

[edgarcosta]

I think we can easily set up a limit on the number of events on the calendar. However, how to pick 1000 if a user has more than that.

I don't follow the addendum. Google calendar sometimes only syncs the calendar once a day, is that the issue?

[edgarcosta]

@poonen, I like your suggestion.

[alreadydone]

Here are two examples: https://researchseminars.org/seminar/ZAG (in Past Talks) https://researchseminars.org/seminar/Iskovskikh I'm sure both events have been updated many days ago to provide the title and abstract (the Mumford event even changed time), but at this moment they still appear in my Google Calendar like so. I checked the downloaded ICS file, and there are no event with these speakers with abstract TBA. So I think maybe Google doesn't clear the whole calendar before syncing the new ICS file gotten from researchseminars.org, but only update/cancel events according to UID matches (and add new events if there is no match). In the cases shown above, maybe Google synced events earlier in the ICS file, reached the event count limit, and simply ignored the rest of the file. For example, I find that the Mumford event is the ~~2282nd~~ 839th event in the file (less than 1111 !), and the Birkar one the 1194th. The file includes 2617 events in total. ICS files generated by researchseminars seems to be ordered by series, and I indeed find that my latest saved series completely fail to show up in Google Calendar. Google seems to be able to remember (cache) calendar by URL, and the cache seems to be shared by all Google users: I removed the researchseminars calendar link from Google yesterday but when I readd it, the TBA events, which don't exist in the ICS file, reappear in Google. The same happens even if I add the calendar link to another Google account.

And yeah, I like @poonen's suggestion too!

[edgarcosta]

The fix suggested by @poonen is now live. I went for two weeks old instead of one week.

Now we also sort the talks in the ICS file by how far away they are from the moment the file is downloaded, thus if you go over some service limit, there is still a chance to get the most relevant talks added/updated.