ADvendio has changed the format of the field Period (Campaign Item: ADvendio__Period__c) to international format. If you prefer the old format of the field you can create a custom formula text field and replace the standard field in the related list.
Period (custom)
IF(DAY(ADvendio__from_Date__c) < 10, "0", "") & TEXT(DAY(ADvendio__from_Date__ c)) & "." & IF(MONTH(ADvendio__from_Date__ c) < 10, "0", "") & TEXT(MONTH(ADvendio__from_Date __c)) & "." & TEXT(YEAR(ADvendio__from_Date_ _c)) & " - " & IF(DAY(ADvendio__until_Date__c ) < 10, "0", "") & TEXT(DAY(ADvendio__until_Date_ _c)) & "." & IF(MONTH(ADvendio__until_Date_ _c) < 10, "0", "") & TEXT(MONTH(ADvendio__until_Dat e__c)) & "." & TEXT(YEAR(ADvendio__until_Date __c))
