Error in Most Frequent Days Test 27

I would like to give some feedback about your answer to test 27 of the Most Frequent Days.

Is the answer correct for test number 27? I find Friday and my research seems to confirm it. 2100 will start and end on a Friday, but you seem to accept Monday as an answer.

From: https://py.checkio.org/mission/the-most-frequent-weekdays/solve/

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