How can remove calendar exception added by mistake?

I added some calendar exceptions have been added by mistake through 1) custom actions, 2) add calendar exceptions 3)select country 4)holidays added.

Now i got that the nest way was to go through calendar groups and add the exceptions from there.
I need to remove some of them or bring back previous calendar settings.
Any idea how to do it? From custom actions apparently you can add calendar exceptions but you are not allowed to remove those exceptions.
Thank you.

Attachment(s)
remove calendar exceptions.PNG