Problem with DateTime matching.

[priyamtheone]

I'm trying to match a certain DateTime value with the current system DateTime. I have a timer and a label on a form. Timer interval is set to 1000. When the form loads, the timer starts ticking. As soon as the current DateTime matches the value of the variable, it shows a message in the label.

When I'm writing the following code, the values don't match even if the current system DateTime is equal to the variable. Label1 isn't showing 'Times Matched':

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Dim dtmNow As DateTime
        dim dtmVar as DateTime=#04/28/2010 03:25:00 AM#
 
            dtmNow = Now
            If dtmVar = dtmNow Then Label1.Text = "Times Matched"
    End Sub

But when I'm writing the same code by parsing 'Now' into DateTime it's working fine.

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Dim dtmNow As DateTime
        dim dtmVar as DateTime=#04/28/2010 03:25:00 AM#
 
            dtmNow = DateTime.Parse(Now.ToString)
            If dtmVar = dtmNow Then Label1.Text = "Times Matched"
    End Sub

Why is it so? The default format of 'Now' is the same as I have stored in dtmVar variable. So there's no question of format mismatch. Does that mean 'Now' is not actually a DateTime property?
Provided, my O.S. is Windows Vista Ultimate and all date/time settings are set to default.
Regards.

[tlhintoq]

DateTime.Now goes down to the 3 digits of milliseconds, regardless of how you display it. So getting an exact match of .Now is going to be (literally) a one in a thousand chance.

You'd be better off taking the time as a string, trimmed to hours, minutes, seconds and comparing that.

DateTime.Now.ToString("HH:mm:ss"); // To get 13:30:45
DateTime.Now.ToString("HH:mm:ss.fff"); // To include miliseconds 13:30:45.678

[priyamtheone]

Thanks for the idea. It's really helpful. This is what I ended up doing:

Dim dtmNow As DateTime
dim dtmVar as DateTime=#04/28/2010 03:25:00 AM#
dtmNow = (Now.ToString("MM/dd/yyyy hh:mm:ss tt"))
If dtmVar = dtmNow Then Label1.Text = "Times Matched"

The other way is to Parse the current DateTime value as I posted.

[Curtis Rutland]

Another simple way to do this is to subtract the two DateTime values, and see how many seconds the resulting TimeSpan object contains.

DateTime dt1 = new DateTime(2010, 5, 12, 9, 38, 0);
TimeSpan difference = dt1.Subtract(DateTime.Now);
double seconds = System.Math.Abs(difference.TotalSeconds);

If seconds < 1 then it is equivalent.

Edit, sorry for the C# code, but it should be pretty self explanatory in VB.NET.

[priyamtheone]

Thank you very much.