CI failing on humanize test

Issue Description

Current CRON CI build on master is failing. The test case tests/test_arrow.py::TestArrowHumanize::test_day is failing on the current master between 7:00-7:59pm EST. The tests pass when run at 8pm EST.

  __________________________ TestArrowHumanize.test_day __________________________
  
  self = <tests.test_arrow.TestArrowHumanize object at 0x7f851fcb8128>
  
      def test_day(self):
      
          later = self.now.shift(days=1)
      
          assert self.now.humanize(later) == "a day ago"
          assert later.humanize(self.now) == "in a day"
      
          # regression test for issue #697
          less_than_48_hours = self.now.shift(
              days=1, hours=23, seconds=59, microseconds=999999
          )
          assert self.now.humanize(less_than_48_hours) == "a day ago"
          assert less_than_48_hours.humanize(self.now) == "in a day"
      
          less_than_48_hours_date = less_than_48_hours._datetime.date()
          with pytest.raises(TypeError):
              # humanize other argument does not take raw datetime.date objects
              self.now.humanize(less_than_48_hours_date)
      
          # convert from date to arrow object
          less_than_48_hours_date = arrow.Arrow.fromdate(less_than_48_hours_date)
  >       assert self.now.humanize(less_than_48_hours_date) == "a day ago"
  E       AssertionError: assert '23 hours ago' == 'a day ago'
  E         - a day ago
  E         + 23 hours ago
  
  tests/test_arrow.py:1851: AssertionError

This test case reproduces it locally:

import arrow

now = arrow.Arrow(2020, 12, 1, 0, 55, 46, 798518)
print("now:", now)

less_than_48_hours = now.shift(
    days=1, hours=23, seconds=59, microseconds=999999
)
print("less_than_48_hours:", less_than_48_hours)

less_than_48_hours_date = arrow.Arrow.fromdate(less_than_48_hours._datetime.date())
print("less_than_48_hours_date:", less_than_48_hours_date)

humanized = now.humanize(less_than_48_hours_date)
print("humanized:", humanized)

# Should be "a day ago"
assert humanized == "a day ago"

System Info

• 🖥 OS name and version: macOS 11.0
• 🐍 Python version: 3.9.0
• 🏹 Arrow version: latest master

[jadchaar]

  ________________________ TestArrowHumanize.test_months _________________________
  
  self = <tests.test_arrow.TestArrowHumanize object at 0x0000000003d52790>
  
      def test_months(self):
      
          later = self.now.shift(months=2)
          earlier = self.now.shift(months=-2)
      
          assert earlier.humanize(self.now) == "2 months ago"
  >       assert later.humanize(self.now) == "in 2 months"
  E       AssertionError: assert 'in a month' == 'in 2 months'
  E         - in 2 months
  E         ?    ^      -
  E         + in a month
  E         ?    ^
  
  tests/test_arrow.py:2160: AssertionError

Hmm, I guess another test failing also for some weird times, coming from https://github.com/arrow-py/arrow/pull/907/checks?check_run_id=1628813383

Ugh good find. Might be related to https://github.com/arrow-py/arrow/issues/749

[systemcatch]

This was one of the problems I encountered in #868. Any value we pick for _SECS_PER_MONTH will result in something being wrong. To fix this properly the “month” duration has to be calculated at runtime imo.

The annoying thing is that this could break installation in some cases. I suggest we find a fix before 1.0.0 or mark the month test as xfail for now.