ansaurus

Question

How to check if two DateTime's occur on the same day

Answer 1

+3 A:

Try

if (newsStory.Date == DateTime.Now.Date) 
{ /* Story happened today */ }
else
{ /* Story didn't happen today */ }

Stephen Newman 2009-10-21 15:27:52

@Lucero - thanks for sorting the formatting out for me :)

Stephen Newman 2009-10-21 16:38:50

Answer 2

+7 A:

if( newsStory.Date == DateTime.Today )
{
    // happened today
}

Dave 2009-10-21 15:27:53

Answer 3

+10 A:

if (newsStory.Date == DateTime.Today)
{

}
else
{

}

Should do the trick.

Cloud 2009-10-21 15:28:07

...if newsStory.Date is actually only the date portion, without time. ;)

Lucero 2009-10-21 15:30:02

...which it is, if newsStory is a DateTime

stevemegson 2009-10-21 15:31:32

@stevemegson +1 :)

Philip Wallace 2009-10-21 15:34:32

Well, from what I can see it may just also be some custom class which happens to expose a `Day`, `Month` and `Year` property, no?

Lucero 2009-10-21 15:52:38

well, DateTime is a part of the .NET Framework Class Library, so while it's *possible* that the OP created his own class that happens to share the same name, you'd have to wonder why he would ask StackOverflow how to use a custom class he created and expect us to magically know how it worked. ;)

Brian Schroth 2009-10-21 16:04:48

@Lucero occam's razor

Dave 2009-10-21 22:41:47

@Dave I really didn't see newsStory as DateTime when I answered the question - maybe due to its naming I thought of it as being a custom class.

Lucero 2009-10-23 07:33:06

@Lucero that's possible however the question title reads 'two DateTimes'. ;) I guess that's where we got that missing type from.

Cloud 2009-10-23 08:10:58

Answer 4

+1 A:

As Guillame suggested, compare values of Date properties.

Anton Gogolev 2009-10-21 15:28:34

Answer 5

+4 A:

If NewsStory was using a DateTime also, just compare the Date property, and you're done.

However, this depends what "today" actually means. If something is posted shortly before midnight, it will be "old" after a short time. So maybe it would be best to keep the exact story date (including time, preferably UTC) and check if less than 24 hours (or whatever) have passed, which is simple (dates can be subtracted, which gives you a TimeSpan with a TotalHours or TotalDays property).

Lucero 2009-10-21 15:29:17

+1 for a more complete answer

JustLoren 2009-10-21 15:34:25

Answer 6

A:

you could use DateTime.Now.DayOfYear

 if (newsStory.DayOfYear == DateTime.Now.DayOfYear)
 { // story happened today

 }
 else
 { // story didn't happen today

 }

Eclipsed4utoo 2009-10-21 15:29:44

I don't think this will work. If today is 10/21/2009, and newsStory is 10/21/2008 - it will return true (I didn't take leap years into account here).

Philip Wallace 2009-10-21 15:33:32

This won't discriminate between yearsnew DateTime(2009, 10, 01).DayOfYear == new DateTime(1900, 10, 01).DayOfYear;

Dave 2009-10-21 15:34:15

You are correct. I totally missed that.

Eclipsed4utoo 2009-10-21 15:51:31

Answer 7

+1 A:

Try this:

newsStory.Date == DateTime.Today

Philip Wallace 2009-10-21 15:29:44

Answer 8

A:

How about

if (newsStory.DayOfYear == DateTime.Now.DayOfYear)
{ // Story happened today
}

But this will also return true for 1st January 2008 and 1st January 2009, which may or may not be what you want.

ShellShock 2009-10-21 15:31:14

Answer 9

+1 A:

well, DateTime has a "Date" property and you could just compare based on that. But looking at the docs it seems that getting that property actually instantiates a new datetime with the time component set to midnight, so it may very well be slower than accessing each individual component, although much cleaner and more readable.

Brian Schroth 2009-10-21 16:01:03

I think a slowdown(if if exists) will be so small it doesn't matter in almost all cases. Certainly a case of premature optimization.

Esben Skov Pedersen 2009-10-22 21:06:09

Agreed - these days I find it's increasingly difficult to shake out premature optimization as the modern coding world is more about readability and maintainability. Old habits die hard!

Peter Bridger 2009-10-23 09:09:57

Answer 10

+1 A:

FYI,

newsStory.Date == DateTime.Today

will return the same compare result as coding

newsStory == DateTime.Today

where newsStory is a DateTime object

.NET is smart enough to determine you want to compare based on Date only and uses that for the internal Compare. Not sure why, and actually having trouble finding documentation for this behaviour.

guck 2009-10-22 20:53:56

Interesting point, thank you

Peter Bridger 2009-10-23 09:08:33

ansaurus

tags:

views:

answers:

How to check if two DateTime's occur on the same day

related questions