foo.cc: In function 'int operator-(const Date&)':
foo.cc:44:9: error: 'year' was not declared in this scope
   44 |  while (year != date2.year && month != date2.month && day != date2.day)
      |         ^~~~
foo.cc:44:31: error: 'month' was not declared in this scope
   44 |  while (year != date2.year && month != date2.month && day != date2.day)
      |                               ^~~~~
foo.cc:44:55: error: 'day' was not declared in this scope
   44 |  while (year != date2.year && month != date2.month && day != date2.day)
      |                                                       ^~~
foo.cc:48:13: error: 'daysOfMonth' was not declared in this scope
   48 |   if (day > daysOfMonth())
      |             ^~~~~~~~~~~

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