Google does not publish how frequently it tried to pull the Caltrics data feed into a user’s Google Calendar. Over the years it has appeared to be once a day around 11am-12noon GMT, but more recently four times a day but at fairly random times.
We can say that if you change your Caltrics selections, it might not be until the next day that you see the changes in Google Calendar and therefore on your phone calendar app.
There is a way to trick Google into forcing an update from Caltrics.
When you connect any subscribed calendar (not just Caltrics) to Google Calendar and you use “Insert By URL”, you can add a random unique parameter at the end of the URL.
The following image shows Google Calendar with the pop menu opened to show how to insert an external calendar “From URL”
And here we see below an example of the Caltrics URL taken from the “My Account” page https://caltrics.com/auth/manage pasted into the “From URL” field. The trick …
…if you want to refresh your Google Calendar entry from Caltrics is to remove the existing entry and it back again BUT adding a unique parameter with a unique value never previously used to the end of the URL so below the parameter “uniqueparameter=123456”, forces Google to reimport the Caltrics calendar because it considers it a new import.