That is a Loooooooooooooonnnnnng shot !

It would surpass the Yosemite websites latest closing date by a fortnight, although not impossible. This data records 29th Dec 1976 [The heatwave year here in the UK, Mmm] but it also records 1st Jan 2000 for the 1999 season that doesn't coincide with the parks page. Quite a few of the dates don't, but not by this margin !

[Off to investigate !]