How often does Google Calendar update it's “Other Calendar” feeds?

Question

I subscribe to a couple of external calendar feeds from my Google Apps calendar and am curious to know how often they get updated.

For example, I have a subscription to my TripIt.com calendar and if I make a change in TripIt, it can be a few days before that change shows up in my Google calendar.

How often does Google Calendar update these feeds?

Answer 1

Google says every few hours, which in my experience means 6-24.

Currently, calendar feeds are automatically updated by Google Calendar every few hours. We understand that some users want to have the ability to refresh the calendars they added manually and we are exploring various ways to enable this.

If the calendar you're subscribing to using Google Calendar isn't refreshed after 24 hours, please send us the calendar address and the detail of the problem so that we can investigate.

Source