Several sets of dates selected: You cannot insert a time bar

What causes this issue?

You have selected several sets of dates. You must select only one set
of dates, for example, basic dates, to be able to insert a new time
bar.

System Response

INCLUDE 'NA_ALLG_NOFUNKTION' OBJECT DOKU ID TX

How to fix this error?

Select the set of dates you want using the menu options <LS>Settings ->
Set of dates</>.

Error message extract from SAP system. Copyright SAP SE.