- Added ``YearMonth.first_day`` and ``YearMonth.last_day`` properties to get the first and last day of the month.
0.4.0
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- ``YearMonth.current()`` now accepts a ``tz`` argument to specify the timezone. - Made ``YearMonth`` instances immutable.
0.3.1
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- Use ``__slots__`` to optimize memory usage.
0.3.0
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- Added ``YearMonth.distance_to()`` method for calculating the distance between two ``YearMonth`` instances.
0.2.0
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- Added support for membership test operators (`in` and `not in`) for checking if a `date` or `datetime` falls within a `YearMonth`. - Improved ``YearMonth.parse()`` performance.