What's the significance of the dates appearing after section names?

[Roadtrekie]

Why is it that sometimes I get dates in parentheses appearing after my
section names in the listing that appears in the Notebooks list on the
left side of the program?

 

[Erik Sojka]

The automated built-in backup system marks a section it has backed up with
the date of the backup and appends that date in parentheses to the section
name to prevent conflicts. Somehow you have either opened up or restored a
previously backed up section.