Excel Date Format Standardization

I have a spreadsheet whose dates now appear in a mix of styles—some show “12/05/23”, others “05-12-2023”, a few are stored as text strings, and a handful are genuine serial numbers. I need the whole column cleaned so every entry follows one consistent, true-date format that Excel recognises natively.

Your task is strictly data cleaning: standardise every date, verify the change with a quick formula check (COUNT, MIN, MAX—whatever you prefer), and hand back a file that requires no manual fixes from me. Feel free to tap Power Query, formula tricks, or simple formatting commands; I only care that the resulting dates sort, filter, and calculate correctly.

Deliverables
• The cleaned workbook with a single, uniform date format (I’m happy with yyyy-mm-dd, but let me know if you spot a better option for the dataset).
• A short change log noting any outliers you had to correct manually.

I’ll review by spot-checking random rows and running a quick DATEVALUE test; if every cell behaves as a genuine date, we’re done.