public IEnumerable <DateRange> SplitByQuarterHour()
{
if (Start.EndOfQuarterHour() == Stop.EndOfQuarterHour())
{
return new[] { this }
}
;
var t = Start.EndOfQuarterHour().AddTicks(1);
return(new[] { new DateRange(Start, t) }.Concat(new DateRange(t, Stop).SplitByQuarterHour()));
}