ValueError: day is out of range for month

Sentry Issue: CONCREXIT-24

ValueError: day is out of range for month
(11 additional frame(s) were not displayed)
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  File "rest_framework/serializers.py", line 260, in data
    self._data = self.to_representation(self.instance)
  File "rest_framework/serializers.py", line 529, in to_representation
    ret[field.field_name] = field.to_representation(attribute)
  File "rest_framework/fields.py", line 1905, in to_representation
    return method(value)
  File "members/api/serializers.py", line 93, in _achievements
    return member_achievements(instance.user)
  File "members/services.py", line 72, in member_achievements
    earliest = earliest.replace(year=earliest.year + mentor_year.year)