Ip Office TIme Settings Error in "Automatic DST"

[w3tmtgpt]

Hi
I have an IP Office with fw 7.0 (23)
The DST does not work !
When I check the button Automatic DST, the field "Clock Forward/Back Settings" show "Add New Entry". When I try to submit a new entry I get an error "System.FormatException: String was not recognized as a valid DateTime."

Tnx