Project Hours can write hour entries to Google Calendar.
Currently you can link to one calender to which all hour entries for your organisation will be written.
When hour entries are updated or deleted, the calendar is synchronized.
To try this out go to the Project Hours Demo environment,
write some hours and check out the Demo calendar below (refresh the page to see new calendar items).
If you are interested you can sign up for a trial account for your organization.
Once you have a trial account, go the menu option Administration, Organisation to setup Google integration. Step-by-step help for setup is available.