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, 1 insertions, 1 deletions

diff --git a/guides/source/debugging_rails_applications.md b/guides/source/debugging_rails_applications.md
index df3003a6a8..f12df093ad 100644
--- a/guides/source/debugging_rails_applications.md
+++ b/guides/source/debugging_rails_applications.md
@@ -683,7 +683,7 @@ Ruby instruction to be executed -- in this case, Active Support's `week` method.
    51:   #
    52:   #   2.weeks # => 14 days
    53:   def weeks
-=> 54:     ActiveSupport::Duration.new(self * 7.days, [[:days, self * 7]])
+=> 54:     ActiveSupport::Duration.new(self * ActiveSupport::Duration::PARTS_IN_SECONDS[:weeks], [[:weeks, self]])
    55:   end
    56:   alias :week :weeks
    57: