Hello @Nathalie,
Yes you can adjust the period in the header of your reports by editing the style of the reports. By selecting the Style/Stijlen on the top,
you will be in the export styles. Select the Stijl 1 for example and in order to access the advanced editing options you will have to click on the address bar and replace the edit word at the end of the address with the word advanced. For example instead of https://live.getsilverfin.com/export_configurations/2982/edit you should write https://live.getsilverfin.com/export_configurations/2982/advanced
If you scroll down you will see a lot of new options. One of them is the Header Text where you can add anything you want to appear in your export.
Regards,
Mike