I am comparing e.NewValues[“Schedule”] != e.OldValues[“Schedule”], in my testing, they are the same value but the if return true in code below, why is that?

DateTime TargetReplenishmentSchedule;
if (!DateTime.TryParse(TextBoxTargetReplenishmentSchedule.Text.Trim(), out TargetReplenishmentSchedule))
{
    ShowJavaScriptMessage("TextBoxTargetReplenishmentScheduleIsNotDate", "Target Replenishment Schedule is not a date!");
    return false;
}
var oldTargetReplenishmentSchedule = e.OldValues["Schedule"];
if (oldTargetReplenishmentSchedule != null)
{
    var old = e.OldValues["Schedule"];
    var nnn = e.NewValues["Schedule"];
    if (e.NewValues["Schedule"] != e.OldValues["Schedule"])
    {
        if (TargetReplenishmentSchedule.Date < DateTime.Now.Date)
        {
            ShowJavaScriptMessage("invalidTargetReplenishmentSchedule", "Target Replenishment Schedule must be on or after today!");
            return false;
        }
    }
}