Informant can sync your data automatically based on the interval you choose.

Go to Informant settings>sync accounts>tap the box at AutoSync.  
We recommend choosing to sync local changes to server immediately and do a full sync every 10 minutes.

Syncing with informant is a push system, not pull. So it will only sync data on the interval you have chosen. For example lets say in Informant if you choose an interval of "sync local immediately and 10 minutes. When you make a change in informant it will complete a sync - that's the immediately part.  It will sync to get new/edited data from other devices that have synced on the timed interval - that's the every 10 minutes part. 

You can always force a sync to complete by going to informant settings>accounts>select the sync service you want to sync and tap the ‘sync’ icon, or tap the menu icon at the bottom right of your calendar view and choose sync.