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DateTime.Compare how to check if a date is less than 30 days old?

Posted by: admin November 29, 2017 Leave a comment

Questions:

I’m trying to work out if an account expires in less than 30 days. Am I using DateTime Compare correctly?

if (DateTime.Compare(expiryDate, now) < 30)

{
     matchFound = true;
}
Answers:

Am I using DateTime Compare correctly?

No. Compare only offers information about the relative position of two dates: less, equal or greater. What you want is something like this:

if ((expiryDate - DateTime.Now).TotalDays < 30)
    matchFound = true;

This subtracts two DateTimes. The result is a TimeSpan object which has a TotalDays property.

Additionally, the conditional can be written directly as:

matchFound = (expiryDate - DateTime.Now).TotalDays < 30;

No if needed.

Questions:
Answers:

should be

matchFound = (expiryDate - DateTime.Now).TotalDays < 30;

note the total days
otherwise you’ll get werid behaviour

Questions:
Answers:

Well I would do it like this instead:

TimeSpan diff = expiryDate - DateTime.Today;
if (diff.Days > 30) 
   matchFound = true;

Compare only responds with an integer indicating weather the first is earlier, same or later…

Questions:
Answers:

Try this instead

if ( (expiryDate - DateTime.Now ).TotalDays < 30 ) { 
  matchFound = true;
}

Questions:
Answers:

Compare returns 1, 0, -1 for greater than, equal to, less than, respectively.

You want:

    if (DateTime.Compare(expiryDate, DateTime.Now.AddDays(30)) <= 0) 
    { 
        bool matchFound = true;
    }

Questions:
Answers:

This will give you accurate result :

if ((expiryDate.Date - DateTime.Now.Date).Days < 30)
    matchFound = true;

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Answers:

Compare is unnecessary, Days / TotalDays are unnecessary.

All you need is

if (expireDate < DateTime.Now) {
    // has expired
} else {
    // not expired
}

note this will work if you decide to use minutes or months or even years as your expiry criteria.

Questions:
Answers:

No, the Compare function will return either 1, 0, or -1. 0 when the two values are equal, -1 and 1 mean less than and greater than, I believe in that order, but I often mix them up.

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Answers:

No you are not using it correctly.

See here for details.

DateTime t1 = new DateTime(100);
DateTime t2 = new DateTime(20);

if (DateTime.Compare(t1, t2) >  0) Console.WriteLine("t1 > t2"); 
if (DateTime.Compare(t1, t2) == 0) Console.WriteLine("t1 == t2"); 
if (DateTime.Compare(t1, t2) <  0) Console.WriteLine("t1 < t2");

Questions:
Answers:

What you want to do is subtract the two DateTimes (expiryDate and DateTime.Now). This will return an object of type TimeSpan. The TimeSpan has a property “Days”. Compare that number to 30 for your answer.

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Answers:

No it’s not correct, try this :

DateTime expiryDate = DateTime.Now.AddDays(-31);
if (DateTime.Compare(expiryDate, DateTime.Now.AddDays(-30)) < 1)
{
    matchFound = true;
}

Questions:
Answers:

Actually none of these answers worked for me. I solved it by doing like this:

  if ((expireDate.Date - DateTime.Now).Days > -30)
  {
    matchFound = true;
  }

When i tried doing this:

matchFound = (expiryDate - DateTime.Now).Days < 30;

Today, 2011-11-14 and my expiryDate was 2011-10-17 i got that matchFound = -28. Instead of 28. So i inversed the last check.

Questions:
Answers:
// this isn't set up for good processing.  
//I don't know what data set has the expiration 
//dates of your accounts.  I assume a list.
// matchfound is a single variablethat returns true if any 1 record is expired.

bool matchFound = false;
            DateTime dateOfExpiration = DateTime.Today.AddDays(-30);
            List<DateTime> accountExpireDates = new List<DateTime>();
            foreach (DateTime date in accountExpireDates)
            {
                if (DateTime.Compare(dateOfExpiration, date) != -1)
                {
                    matchFound = true;
            }
            }

Questions:
Answers:

Assuming you want to assign false (if applicable) to matchtime, a simpler way of writing it would be..

matchtime = ((expiryDate - DateTime.Now).TotalDays < 30) ? true : false;