User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0 Build ID: 20130307023931 Steps to reproduce: Well, basically just create a Recurring event, custom, weekly, interval 2, select all days (MO-SU) And create. Actual results: For example, I create it starting from 2013-1-1 and the first occurences are 7th, 8th, 9th, 10th, 11th, 12th and 13th (+1st since lightning creates event for the selected day too). Expected results: Occurences should be 1st, 2nd, 3rd, 4th, 5th, 6th and after that the 2 week interval. Google implements it this way, and also if you import an iCal file with this rule (RRULE:FREQ=WEEKLY;INTERVAL=2;BYDAY=SU,MO,TU,WE,TH,FR,SA and DTSTART;20130101T080000Z), it is imported correctly. So the issue is only when you create it in the lightning.
In Bug 566149 has been decided that the Edit dialog must keep the until date when changing the start date so marking this as duplicate.
Sorry wrong bug. Confirm this one anyway.