Google Drive Files
By default, offline access to Google Docs, Sheets, and Slides is enabled for organisations.
Users can turn it on or off for their own accounts as needed. Organisation can simply do so by enabling offline access for all users via the admin console.
What about Gmail?
To work offline in Gmail, you need a Chrome browser version 61 or later. Then, Gmail offline must be turned on from the admin console.
NEVER enable the offline mode for Gmail on a shared device.
To work offline in Calendar: Open Google Calendar. Click the Gear, select Offline. Voila! Now your offline sync is confirmed.
What if Google Calendar is not an installed app from the Chrome Web Store?
You’ll need to install it first. Then, in the message box prompt “Enable Google Calendar Offline”, click Enable.
After the synchronising is completed, you can have more than one calendar synchronised by clicking the Offline settings link then placing a check-mark to additional calendars to sync offline. Make sure to click the save button when you’re all set.