HalleyInteractive
commented
10 years ago You can enable the Google Calender API in the cloud console. It seems pretty straight forward.
https://developers.google.com/google-apps/calendar/?csw=1 http://developers.google.com/apis-explorer/#p/calendar/v3/
GriffinSauce
After planning a date for a period the following is shown:
"Add to calender" might be able to use OAuth, otherwise provide iCal?
"Mail it" should provide a standard e-mail subject containing groupname and date, the body might be a funny random (see #8)
"Replan" should give a warning about people having already set up calendars and such, double dialog check to make sure, and immediately send out an e-mail to groupmembers cancelling the previous date. After that simply undo the planned date and return to the availability/planning view.