Incorrect dates not being corrected

[CooperT]

This issue has come up before:

Two funny things in PanoramaX

Perhaps you think, as I did, that 2/30/19 is not a valid date. But, it turns out, that in PanoramaX 2/30/19 is equivalent to 3/2/19. Although 2/30/20 is equivalent to 3/1/20. So datepattern(date("2/30/19"),"Month dd, yyyy") ==> March 2, 2019 but datepattern(date("2/30/20"),"Month dd, yyyy") ==> March 1, 2020 and datepattern(date("4/31/19"),"Month dd, yyyy") ==> May 1, 2019. But exceeding 31 for day will return an error. For some legal purposes, one year after 2/29/16 will be March 1, 20…