Date with year 1988 doesn't work correctly when setting year

[daxhuiberts]

Description of the Issue and Steps to Reproduce:

When I have a moment object of which the year is 1988 (e.g. moment("1988-02-10")) and I change the year (e.g. date.year(2017)). Then the day of month is always changed to the last day of the month.

Environment:

Chrome Version 61.0.3163.100 (Official Build) (64-bit) on MacOS Sierra Version 10.12.6.
Examples can be run on the javascript console on the momentjs homepage.

Some incorrect examples::

moment("1988-02-10").year(1999).toString() // => "Sun Feb 28 1999 00:00:00 GMT+0100"
moment("1988-09-25").year(2017).toString() // => "Sat Sep 30 2017 00:00:00 GMT+0200"

Some good working examples:

moment("1989-02-10").year(1999).toString() // => "Wed Feb 10 1999 00:00:00 GMT+0100"
moment("1987-09-25").year(2017).toString() // => "Mon Sep 25 2017 00:00:00 GMT+0200"

[emilebosch]

It happens with all leap years, not just 1988.

[emilebosch]

so the original use case was that we wanted to calculate the next birthday of the user. It yielded incorrect results

[mattjohnsonpint]

Dup #4258. Will track there. Thanks.

[mattjohnsonpint]

Actually, dup #4024 and fix pending in #4255.