Chart properties - Guide series
General tab, Select Columns diagram, for example
Data tab / Select a Date data field for the Categories
Guides tab / Dynamic option /
Edit guide series
A color can be selected for the guide, e.g. to highlight the month
Color the complete area
The entire area is colored in.
Define an internal for the series pattern here.
Duration of series
The amount of repeats can be defined here. After this amount, the highlighting will no longer be shown.
No end date
If an end date is not selected, the highlighting applies to the entire diagram.