We do not need a generalized date mapping function to verify the claim, we only need to verify specific events/dates, and even for those we only need to verify

We do not need a generalized date mapping function to verify the claim, we only need to verify specific events/dates, and even for those we only need to verify a single inequality. OTOH, looking at the data, events are dispersed over more than a month (range 124 - 86 = 38 days), so it is possible an earlier date was pushed later, where it fits better - one cannot reliably deduce month from year + day of month.