For a very large set of dates it's likely that Sequence is the culprit for slowing it down.

Great that this works for you. An alternative to having 10's of thousands of rows is to have a table with dates along the top, minutes on the bottom - the calculation speed will be similar but it makes it a little more manageable to view.

Rolling60minsample_v4 - Copy.xlsx

It's still easy to find the MAX value, but finding the corresponding time through formulas is more complex (although you can manually search for the Max result to see the date/time)