Excel Keeps Changing Dates Sequentially

Helloavatexrs​, Excel normally does not change manually entered dates after reopening a workbook. If values such as 1/4, 1/8, 1/12, 2/6 become 1/4, 1/5, 1/6, 1/7, it is usually because the cells are part of a series or table that automatically fills sequential dates. Make sure the cells do not contain formulas, clear the cells and type the dates manually without using the fill handle, and if needed, format the cells as Text before entering the dates.

Microsoft documentation: https://support.microsoft.com/en-us/office/create-a-list-of-sequential-dates-aa1c0fa7-c76a-4762-8bc9-46f1691defec