The widgets in DigiCal are scheduled to update every 30 minutes with a repeating alarm, but only when the system is running so it doesn't use any power when the device is sleeping. This works great most of the time, but because Android clears all alarms when an app is forced to stop or restart, if you have (automatic) task killers installed or force stop DigiCal manually, the widgets won't update until you manually refresh it once.
If you have issues with widgets not refreshing, please make sure don't have a task killer installed or configure the task killer to leave DigiCal alone.
We have add a workaround by forcing widgets to refresh 4 times a day so the issue is less visible; but even then, force stopping DigiCal will cause widgets to be out of sync for up to 6 hours.
"Stopping an application is there for the user to stop everything associated with it -- processes, alarms, services, notifications, etc. They will not be restarted until someone explicitly does so." - Dianne Hackborn, Android framework engineer.