For more information see: Exchange Outlook Calendaring Problems.
Exchange itself is usually not the root of the problem, the mail clients (Active Sync, i OS devices, Blackberries, i Cal) and their connectivity protocol tend to be the culprits. For instance, if someone accepts a meeting at 9am on an i Phone and a delegate declines it at am on a PC, but the i Phone is out of signal range and doesn't sync the meeting until say am., what happens to the meeting?
If you want to send the changes back to Google Calendar, you need to export your Outlook Calendar.
Google officially announced "Google Sync End of Life", including the Google Calendar Sync, last year.
Google Calendar updates feed information once every 8 hours.I’m using i Cloud with Outlook to synch my Contacts and Calendar with my i Phone and i Pad.This all worked without any issues until I upgraded to Windows 10.Outlook will periodically check the Google Calendar for updates, and if any new or modified events are found, they will be downloaded and displayed alongside with your Outlook appointments. Remember that the Google Calendar imported in this way is read-only, the lock icon is displayed in the lower right hand corner of all imported Google Calendar's events, meaning they are locked for editing.Changes made in Outlook are not synced with your Google Calendar.And on 1 August 2014, our good old Google Calendar Sync has finally come to an end, alas.