You can try this,
If CTime({Table.Item_Created_Timestamp}) > CTime(13, 00, 00)
Then Date({Table.Item_Created_Timestamp}) + 1 + CTime(08,00,00)
Else {Table.Item_Created_Timestamp}
You can try this,
If CTime({Table.Item_Created_Timestamp}) > CTime(13, 00, 00)
Then Date({Table.Item_Created_Timestamp}) + 1 + CTime(08,00,00)
Else {Table.Item_Created_Timestamp}