Excel even implemented lotus 1-2-3 bugs to ensure compatibility: see 1900-02-29 https://answers.microsoft.com/en-us/msoffice/forum/msoffice_excel-mso_other-mso_

Excel even implemented lotus 1-2-3 bugs to ensure compatibility: see 1900-02-29 https://answers.microsoft.com/en-us/msoffice/forum/msoffice_excel-mso_other-mso_2007/bug-1900-feb-29th-is-a-valid-date-for-ms-excel/682400e0-708e-4dd7-aa22-d72bcbd16443 https://answers.microsoft.com/en-us/msoffice/forum/msoffice_...