I have not had the opportunity to verify this, but I know that QDateEdit implements QAbstractSpinBox, so you can call
myDateEdit.setWrapping(True)
which should fulfill what you want.
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Update:
The term for this behavior is apparently called “rollover”, and here is the realization of one person who (again, I have not tested it) seems to be another potential solution:
Rollover QDateEdit
He emphasizes that its implementation does not take into account minimum or minimum dates.
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