Comparing future dates in C#

Question

I know this is probably a pretty simple question, but i am trying to write a function that returns a bool value of "true" if a date passed is in the future, like this:

bool IsFutureDate(System.DateTime refDate)
{
    if (refDate > DateTime.Now)  // This doesn't seem to work
        return true;
    return false;
}

Anyone tell me who to write a function like this that actually works?

Thanks

Answer 1

DateTime handling is always tricky.

I have summarized what's been mentioned so far and made this post Community Wiki.

Time Zone Handling

static bool IsFutureDateTime(DateTime dateTime) {
   // NOTE: ToUniversalTime() treats DateTimeKind.Unspecified as local time. We
   //       therefore insist that the input kind is always specified.
   if (dateTime.Kind == DateTimeKind.Unspecified) {
       string msg = "dateTime.Kind must not be DateTimeKind.Unspecified.";
       throw new ArgumentException(msg, "dateTime");
   }

   return dateTime.ToUniversalTime() > DateTime.UtcNow;
}

Comparing Dates Only

static bool IsFutureDate(DateTime date) {
    return date.Date > DateTime.Today;
}

Answer 2

The only thing I can think of is you might get undefined behaviour if refDate == today.

DateTime.Now includes the time. If refDate if for say today at 3:00 and you run it at 2:00 it will return true. If you run at 4:00 it will return false.

Compare it to DateTime.Today and that will just return the date, preventing the time of day influencing it.

Other than that it should all be fine..

Answer 3

bool IsFutureDate(DateTime refDate) {
    DateTime today = DateTime.Today;
    return (refDate.Date != today) && (refDate > today);
}

Answer 4

The TimeSpan structure is helpful:

http://msdn.microsoft.com/en-us/library/system.timespan.aspx

How precise do you need it to be? Down to the millisecond?