You are implementing time sheets and you would like to use business rules to default values such as start time, end time, time type and so on.
You have then configured a business rule using the object Employee Time Sheet Day but the business rule does not seems to work.
SAP SuccessFactors Employee Central (EC) - Time Sheet
The object Employee Time Sheet Day only supports reading data for validation purposes but it won't be possible to default any value in it.
If you require this to be supported, please create an enhancement request according to the KBA 2090228.
KBA , LOD-SF-EC-TIM , Time Off , Product Enhancement