Membership end date incorrectly calculated for multi-year fixed with rollover

To reproduce:
1 Create a membership type

• duration = 5 years
• rollover = 1 July
• fixed = 1 April

2) create membership starting on 8 January 2015

3) expected = that because we are after the roll over date they will get a membership lasting until 5 years after the next fixed date -ie 1 April 2015 + 5 = 31 March 2020
actual = 31 March 2019

Expected behaviour is explained here
http://book.civicrm.org/user/current/membership/defining-memberships/

However it is not clear what the START date should be - ie. is it

• 8 Jan 2015 because that is when it starts (but they are getting a small add on free - ie. 8 Jan to 31 March)
• 1 April 2014 - because that is the start of the year which they are being 'credited' *** - this is what it is currently being set to
• 1 April 2015 - because that is the start of the year they have purchased

There have been a handful of issues on this over the years with this being the latest https://issues.civicrm.org/jira/browse/CRM-13786 - that issue states it should be start_date + period and that IS what is currently happening - so, is the start date being set correctly.

Newsflash - idea entered my brain - I'll check what happens with 1 year WRT start_date