Keep or Remove data (duplicates) based on time of entry?

indeed, when you have a timestamp column, you can sort your data descending on dates (newest first) and then remove duplicates (using all or some of the data columns, but not using timestamp column).

To automatically add timestamp to added data you could use a macro - namely Worksheet_Change event handler - there are many examples on the forum and in the web. I will not try to write next one, especially as we don't know your data layout and where could be this extra column (for timestamp) located. See for instance https://www.excelforum.com/excel-pro...-the-code.html

The second idea (also VBA based) would be to use the same event and not write timestamp but automatically remove data (from the set preexisting in a worksheet) which is duplicated in newly pasted rows.