sync - How can I synchronise my Outlook Calendar with Google Calendar (preferably using a free/open source tool)?

How can I synchronise my desktop Outlook calendar with my Google Calendar (Outlook -> Google)?

I saw the question Free tool for Synchronizing Google Contacts and Calendar with Outlook, but the solution that was suggested there is no longer available - Google Sync End of Life.

There are tools that required a payment, like SyncMyCal, gSyncit and OggSync, but I am looking for a free / open source solution.

One can download Google sync, but when trying to use it there's an error:

For now, I use OggSync to synchronise, but as a freeware it allows to synchronise manually only, not automatically, so I have to remember to synchronise after every change.

I checked Mozilla Sunbird, but I couldn't find any relative posts on how to synchronise Outlook -> Google using it.

Just to be clear: I'm not looking for software; I am looking for a solution. What can I do if sometimes software is a solution?

Answer

The synchronisation is sort of no longer needed. You can simply open your Google calendar in Outlook and overlay it. To do this, go to the calendar settings in Google and click on the ICAL button. Copy the URL.

Then go to Outlook and select the "Open Calendar" button from the Ribbon, then "From Internet". Enter the URL you copied above. It now displays your Google calendar next to your Outlook calendar. Click the little arrow next to the Google Calendar name to overlay it.

Google seems to be deliberately not providing these instructions next to the instructions for other OSes and applications. They must have fallen out with Microsoft, very childish!

I am not sure how to make it work in reverse though (add the Outlet calendar to Google) - I expect this is possible if you know the URL of your calendar on the Exchange server.