How to default effective start date on Jobs/Position only when creating or updating / not correcting

Summary:

I have defaulted the Effective Start date to sysdate on the Job page in Redwood Express mode using this function found in this community [[ (new Date()).toISOString().substring(0, 10) ]]

while this works for Update and Create mode / it also defaults to sysdate in correct mode / virtually updating the job / not correcting it. I see that there are rules that can be set based on values of other fields - but I do not know how to specifiy that I want to leave the current date in Correct mode / Default to sysdate in Update and Create mode - can somebody point me to the correct sintax / way to do it? Thank you