If you accidentally clear a calendar in Google, and you sync your Google calendar with Outlook using the Google sync client, to restore your data in Google do the following:

1.Uninstall Google sync client for Outlook from your desktop
2.Reinstall, then sync from Outlook to Google.   

If you synced the deleted events from Google to Pocket Informant, at this time, you can do a reset sync to restore your data to Pocket Informant.