Should AS::TimeWithZone#since and #+ be the same method?

I was reading the docs for TimeWithZone (http://edgeapi.rubyonrails.org/classes/ActiveSupport/TimeWithZone.html) and noticed that two different methods can be used to add an interval: +(other) and since(other).

I ran some manual tests (copied below) and found that the two methods return the same result in almost every case.

The only case where they differ is when TimeWithZone wraps a DateTime and the "other" value passed to "since" is in a form like "1.month":

    dt = DateTime.new(2014, 12, 01, 22, 00, 00).in_time_zone
  dt + 1.month # => Thu, 01 Jan 2015 17:00:00 EST -05:00
  dt.since 1.month # => Wed, 31 Dec 2014 17:00:00 EST -05:00

However, this usage of "since" is explicitly discouraged by the documentation of DateTime#since (https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/date_time/calculations.rb#L86L88):

  # Returns a new DateTime representing the time a number of seconds since the
  # instance time. Do not use this method in combination with x.months, use
  # months_since instead!

And indeed, following this recommendation the correct result is returned:

  dt.months_since 1 => Thu, 01 Jan 2015 17:00:00 EST -05:00

Therefore, my proposal is to remove the method definition of TimeWithZone#since and instead replace it with a simple alias_method :since, :+

The rationale is that the only case where they differ is a case that is explicitly discouraged as "wrong".
If you think this is a good idea that will make the code clearer to understand, then I will open a PR with a set of tests that demonstrate that the two methods are equivalent in every other case.

Thanks!