What is written under a thumbnail

Under every thumbnail is one line. What it says is a setting, and it is worth knowing which of the two answers you are reading.

A date, or a name

By default the line is the date the item's content was made — the same date that decided which month the item is in. Switch Show creation date as item name off in the settings and it becomes the file name instead.

Which is better depends on what you are doing. The date is the better label while you are looking for a moment in time, and it is the label that explains the order of the grid. The file name is the better one while you are looking for a particular file you can half remember the name of.

A file name too long for the column is shortened. Hold the pointer over it to read the whole thing.

The mark on an uncertain date

Some items are placed by their file dates because the file itself carries no capture date. Their position in the grid is a guess and can be wrong by years.

Switch Mark items without a capture date on and those items are marked, so you can see at a glance which parts of the order to trust. It is off to begin with, because in a folder of downloaded files nearly everything would carry the mark and a mark on everything says nothing.

Where the dates come from explains when this happens and why.