I’ve added a Calendar Export to my Hotmail Account so I can view it in outlook.com. Works great, but unfortunately Outlook doesn’t seem to update. According to https://stackoverflow.com/questions/538081/set-update-limits-on-icalendar-feed there is a Option called " X-PUBLISHED-TTL" which should be used in the ICal-Export. Maybe this is something Phabricator’s Calendar can set?
Bonus Points: I really find Phabricators Algorithm for observing Repositories nifty. Maybe something similar could be implemented for this TTL?