void UpdateMaxDate()
{
if (_dialog != null)
{
//when not to specify 23:59:59,last day can't be selected.
_dialog.DatePicker.MaxDate = (long)AddDatePicker.GetMaxDate(Element).AddHours(23).AddMinutes(59).AddSeconds(59).ToUniversalTime().Subtract(DateTime.MinValue.AddYears(1969)).TotalMilliseconds;
}
}
void UpdateMaxDate()
{
_picker.MaximumDate = AddDatePicker.GetMaxDate(Element).ToNSDate();
}