Why is the list of items in a folder separated by date ranges such as 'last 30 days'?

This is what the contents of one of my iCloud Drive folders looks like. For some reason Mac separates the file name with indicators such as "Previous 30 days" and "Earlier", while some items, those at the top, do not appear to be affected by this. There is no way for me to sort these items by name. This separation also applies in Column and Icon views.

Is there any reason for this? I find it harder to find the items I'm working on. Is there any way to turn it off?