HI ALL
I got the below error canu pls resolve me .
Error: Compile Error: Illegal assignment from Map<Id,Contact> to Map<Id,viswa.Contact> at line 3 column 5



trigger Email_Check_On_Contact on Contact (before update) {
  Map<Id,Contact> o = new Map<Id,Contact>();
    o = trigger.oldMap;
    for(Contact newcont: trigger.new)
    {
      
        if(newcont.Email != o.get(newcont.Id).Email)
        {
            newcont.Email.addError('Email cannot be changed');
        }
    }
}

Why we can add time-dependent workflow actions for

           1) When a record is created, or when a record is edited and did not previously meet the rule criteria

            2) Only when a record is created

but Why we cannot add time-dependent workflow actions for Every time a record is created or edited ?

please give me explanation