Add to Calendar creates item with incorrect date/time

[morganestes]

After #70 fixed the date of the WordCamp to display correctly, when I use the "Add to Calendar" option on the new date it tries to add the event to the calendar with the date that previously appeared.

For example, WordCamp OKC is scheduled for Jul 30, 2016; before #70 it displayed as Jul 29, now it displays Jul 30, but the calendar item is created for Jul 29 from 7-8 p.m.