Fix inconsistent results when parsing large durations and constructing durations from code

    ActiveSupport::Duration.parse('P3Y') == 3.years # It should be true

Duration parsing made independent from any moment of time:
Fixed length in seconds is assigned to each duration part during parsing.

Changed duration of months and years in seconds to more accurate and logical:

 1. The value of 365.2425 days in Gregorian year is more accurate
    as it accounts for every 400th non-leap year.

 2. Month's length is bound to year's duration, which makes
    sensible comparisons like `12.months == 1.year` to be `true`
    and nonsensical ones like `30.days == 1.month` to be `false`.

Calculations on times and dates with durations shouldn't be affected as
duration's numeric value isn't used in calculations, only parts are used.

Methods on `Numeric` like `2.days` now use these predefined durations
to avoid duplicating of duration constants through the codebase and
eliminate creation of intermediate durations.

1 files changed, 2 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/core_ext/integer/time.rb b/activesupport/lib/active_support/core_ext/integer/time.rb
index 4a64872392..66ac3ca1b4 100644
--- a/activesupport/lib/active_support/core_ext/integer/time.rb
+++ b/activesupport/lib/active_support/core_ext/integer/time.rb
@@ -18,12 +18,12 @@ class Integer
   #   # equivalent to Time.now.advance(months: 4, years: 5)
   #   (4.months + 5.years).from_now
   def months
-    ActiveSupport::Duration.new(self * 30.days, [[:months, self]])
+    ActiveSupport::Duration.new(self * ActiveSupport::Duration::PARTS_IN_SECONDS[:months].to_i, [[:months, self]])
   end
   alias :month :months
 
   def years
-    ActiveSupport::Duration.new(self * 365.25.days.to_i, [[:years, self]])
+    ActiveSupport::Duration.new(self * ActiveSupport::Duration::PARTS_IN_SECONDS[:years].to_i, [[:years, self]])
   end
   alias :year :years
 end