Question

I need to determine duration between two DateTimes in minutes.

However, there is a slight twist:

• exclude weekends
• only count minutes
  which are between 7:00AM and 7:00PM.
  for example: [09/30/2010 6:39:00
PM] - [09/30/2010 7:39:00 PM] = 21
Minutes

I’m just having a hard time coming up with a decent way to do it and would appreciate if anyone can suggest something.

Thanks.

---

Edit:

I ended up going with dtb’s solution. There is only one special case which needed to be taken care of: if end time is after 7:00PM, count the minutes from 7:00AM to the actual end time.

This is how I modified it:

var minutes = from day in start.DaysInRangeUntil(end)
                where !day.IsWeekendDay()
                let st = Helpers.Max(day.AddHours(7), start)
                let en = (day.DayOfYear == end.DayOfYear ? 
                            end :
                            Helpers.Min(day.AddHours(19), end)
                            )
                select (en - st).TotalMinutes;

Again, thanks for the help.

Answer 1

You can, of course, use LINQ:

DateTime a = new DateTime(2010, 10, 30, 21, 58, 29);
DateTime b = a + new TimeSpan(12, 5, 54, 24, 623);

var minutes = from day in a.DaysInRangeUntil(b)
              where !day.IsWeekendDay()
              let start = Max(day.AddHours( 7), a)
              let end   = Min(day.AddHours(19), b)
              select (end - start).TotalMinutes;

var result = minutes.Sum();

// result == 6292.89

(Note: You probably need to check for a lot of corner cases which I completely ignored.)

Helper methods:

static IEnumerable<DateTime> DaysInRangeUntil(this DateTime start, DateTime end)
{
    return Enumerable.Range(0, 1 + (int)(end.Date - start.Date).TotalDays)
                     .Select(dt => start.Date.AddDays(dt));
}

static bool IsWeekendDay(this DateTime dt)
{
    return dt.DayOfWeek == DayOfWeek.Saturday
        || dt.DayOfWeek == DayOfWeek.Sunday;
}

static DateTime Max(DateTime a, DateTime b)
{
    return new DateTime(Math.Max(a.Ticks, b.Ticks));
}

static DateTime Min(DateTime a, DateTime b)
{
    return new DateTime(Math.Min(a.Ticks, b.Ticks));
}