Dear Bob,
I understand how worrying it is when names land in the wrong place, especially when important data could be missed. As a forum moderator, I genuinely wish I could directly access your account or delve into the backend systems to diagnose and fix this for you. Unfortunately, my role here is limited to providing general guidance and solutions that can be applied by users. From my research, Excel probably is not converting the surname MARCH into a date. The PivotTable is likely matching MARCH to Excel’s built-in month custom list, which can place it in calendar order ahead of ordinary surnames. Formatting the source column as Text does not prevent that behavior because the value is still text matching a month name.
For you receiving the best suggestion and guidance for this issue, I recommend you publish your workflow in the Excel | Microsoft Community Hub. This forum is dedicated to Excel and is actively monitored by power users, Microsoft partners, and engineers who can provide step-by-step guidance and share best practices.
I apologize for redirecting you to another community, as I may not have the necessary skills and experience to solve your Excel issue.
Thank you for your patience and understanding during this process. For any questions or further assistance in the future, please feel free to reach out again at any time. Not only will I be happy to assist you, but also all the moderators of the Q&A forum will do their best to provide support and guidance.
I hope everything will be resolved soon. Have a great day.