The CalendarAgent service takes all my CPU, every time I get a network connection. This is really annoying in many situations (one example: closing the lid for 2 minutes, change train and open it again) and slows down everything.

I already tried many solution:

  • reset the calendars
  • clear the cache files
  • change configs for the accounts
  • renice the CalendarAgent process
  • set ALL my accounts to manual refresh (Command + R)

The service doesn't care; if it's active it will hog the CPU. Only alternative is to disable the service; but, what a surprise, the Calendar app won't work anymore and crash.

I have calendars in sync with iCloud, Exchange, Google.

I'm struggling with this issue and would really like to take control back on this annoying process. I am fine with having to refresh manually the calendars but at least decide when to hog the CPU with updates.

How can I solve this?

OSX: El Capitan

  • try to disable synchronization to test defaults -currentHost write com.apple.syncservices SyncingDisabled YES change it back with NO ...Alternatively just disable calendars one by one to see which one is doing it
    – Ruskes
    Sep 30, 2018 at 20:16
  • It still pops up after 1 minute the network/wifi connection is enabled and takes a lot of CPU. It seems to run a little shorter, at least, but the undesired behaviour is still there. I really don't understand what it is doing, and also don't get why it ignores my "update manually" setting... (if Syncing is what it is actually doing, during those CPU bumps) Sep 30, 2018 at 20:35
  • did you disable all calendars and it stops ?
    – Ruskes
    Sep 30, 2018 at 20:41
  • I disabled all of them now: it still hogs the CPU but for shorter time now (around 10 seconds). I suppose that syncing is just part of the problem; it is doing also something else. I really would like to get this service to run just once per-day; I don't need this continuous updating/operations. To notice: it always spikes (but for shorter) also immediately after disabling the network/wifi. Sep 30, 2018 at 21:00

1 Answer 1


I had the same problem with El Capitan, High Sierra, and now Mojave (seems to have worsened). For me the removing the google delegation seems to have solved the issue: How can I diagnose or fix the CalendarAgent occupying a whole CPU on Mountain Lion?

  • 1
    Yeah all that piece of software sucks. And there is not a single decent alternative, free of charge, on the AppStore. I cannot get rid of the Google calendars, those are my main ones! 🙁And Exchange ones for work. And... even removing the Google ones it is still sluggish, spikes at 100% every single time I get a network connection or wake from standby...... I am seriously looking to get totally rid of CalendarAgent process and find some alternative/**working** software... Jan 23, 2019 at 14:00

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .