[perl #127161] DateTime methods .earlier and .later allow negative years, days, seconds but not months (.earlier(months => -1))

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# New Ticket Created by  Alex Jakimenko 
# Please include the string:  [perl #127161]
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# <URL: https://rt.perl.org/Ticket/Display.html?id=127161 >


These are not working:

Code:
say DateTime.new(‘2016-01-31T05:00:00Z’).earlier(months => -1)

Result:
Month out of range. Is: 0, should be in 1..12
  in block <unit> at /tmp/CfLpbWf_RV line 1

Code:
say DateTime.new(‘2016-01-31T05:00:00Z’).later(months => -1)

Result:
Month out of range. Is: 0, should be in 1..12
  in block <unit> at /tmp/jdJBjXGCdA line 1


But all these do:

Code:
say DateTime.new(‘2016-01-31T05:00:00Z’).earlier(years => -1)
Result:
2015-01-31T05:00:00Z

Code:
DateTime.new(‘2016-01-31T05:00:00Z’).earlier(days => -1)
Result:
2016-02-01T05:00:00Z

Code:
DateTime.new(‘2016-01-31T05:00:00Z’).earlier(seconds => -1)
Result:
2016-01-31T05:00:01Z

Code:
say DateTime.new(‘2016-01-31T05:00:00Z’).later(seconds => -1)
Result:
2016-01-31T04:59:59Z


Personally I think that negative values should be allowed (so
TIMTOWTDI-ish!).