If you create a new ScheduledItem object and look at the StartDate - it's 1/1/1990 - why? This has just caught me out when trying to evaluate whether the dates have been set or whether they're, what I was guessing would be, MinDate.
Normally, if scheduling is activated on a SharePoint list, while adding a new item into the list, there are 2 options in the scheduled start date. Its either a "Scheduled Date" or "Immediately".
If a new list item is created to schedule immediately, these items would have a start date that is prior to the current date and internally SharePoint keeps this as "1/1/1990" to make it before the current date and to get it approved it in the next cycle asap. A similar explanation is given in the msdn article here which you can go through.