Excel Reformat Dates & Remove Duplicates

I have an Excel workbook where every date needs to appear in the strict ISO style — YYYY-MM-DD. Once the dates are fixed, any row that is an exact duplicate should be completely removed so the file contains only unique records. No further sorting, summaries, or other transformations are required.

Please return the updated spreadsheet showing the corrected date column and the cleaned data set. A quick rundown of what you changed (just a sentence or two) will help me verify the work.