C#: efficient way to check if datetime.Day within a certain range?

Question

Given a DateTime, I want to check if the .Day is between a number, say between 15 and 19.

So 9/16/2013 passes, but 9/20/2013 fails.

Thanks,

@meorfi: Don't worry. Seems this question got more than enough answers :D — huMpty duMpty, Sep 10 '13 at 14:28
@huMpty duMpty, there was no answer at the moment when I noticed the problem... — mihai, Sep 11 '13 at 11:17

makim · Answer 1 · 2013-09-10T14:05:41.610

11

Including

var date = DateTime.Now;
if (date.Day >= 15 && date.Day <= 19)
{
        return true;
}

Excluding

var date = DateTime.Now;
if (date.Day > 15 && date.Day < 19)
{
        return true;
}

I´m not 100% sure which one is right ;)

edited Sep 10 '13 at 14:05

answered Sep 10 '13 at 13:57

makim

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This won't work if now is 30 september for instance; – Rob van der Veer Sep 10 '13 at 13:57
4

@RobvanderVeer: Isn't that the desired behavior? – PinnyM Sep 10 '13 at 13:58
2

shouldn't it be `<= 19` – Habib Sep 10 '13 at 13:59
can you please explain me why? don´t see it ^_^ – makim Sep 10 '13 at 13:59
@sine, I am not sure as well, but its an easy fix for the OP. +1 though :) – Habib Sep 10 '13 at 14:00
1

@Habib I'm saying that the `date.Day` checking does not take account of the month. – Rob van der Veer Sep 10 '13 at 14:01
1

@RobvanderVeer: The OP mentioned no requirement about month checking... – PinnyM Sep 10 '13 at 14:02
@RobvanderVeer, from the question it appears that is the desired behaviour – Habib Sep 10 '13 at 14:02
i removed the <= >= I think between is exclusive but I´m also not sure about this just found this http://www.urch.com/forums/gmat-math/126565-does-between-x-y-include-x-y.html – makim Sep 10 '13 at 14:02
@sine: This depends on semantics commonly used for the context under discussion. I would disagree with the posted link's conclusion in this case. – PinnyM Sep 10 '13 at 14:04
I´ve updated the answer with both possibilities! But I think you´re right it should be including the days – makim Sep 10 '13 at 14:07

Cameron Tinker · Answer 2 · 2013-09-10T16:57:38.837

3

Something like this should work:

var date = DateTime.Now;
return (date.Day >= 15 && date.Day <= 19);

Since this is just a range, you can use less than or greater than operators for comparison. Also, you might use the >= or <= operators for including the start or end day.

An alternative approach based on the fact that only one predicate must be true for the date to be out of the range:

var date = DateTime.Now;
return !(date.Day < 15 || date.Day > 19)

edited Sep 10 '13 at 16:57

answered Sep 10 '13 at 13:58

Cameron Tinker

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+1 The second approach is the most efficient. – Rotem Sep 10 '13 at 14:18
Thanks! I based my second approach on your comments. – Cameron Tinker Sep 10 '13 at 14:27
1

There is no need to have `if(...)return true; else return false;`. Whenever you see that you can just replace it with `return ...;` In this case, sense it's reversed, it's just `return !...;` – Servy Sep 10 '13 at 14:29

score 2 · Answer 3 · answered Sep 10 '13 at 13:58

2

if((DateTime.Today.Day >= 15) && (DateTime.Today.Day <= 19))
{
    //do something
}
else
    //do something else
}

answered Sep 10 '13 at 13:58

damaltor

51
3

mihai · Answer 4 · 2013-09-10T14:26:15.777

1

Edit: (because of the error which you can see in the picture (in comments) i wasn't able to post the answer.)

private bool IsInRange(DateTime yourDate, DateTime lowestRange, DateTime highestRange) {
   return yourDate.Day >= lowestRange.Day && yourDate.Day <= highestRange.Day; 
}

edited Sep 10 '13 at 14:26

answered Sep 10 '13 at 14:03

mihai

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Why check both if one is already false? Quite an overcomplication. – Rotem Sep 10 '13 at 14:07
sorry, i cannot submit the full answer because the stackoverflow site block my method which contains the word `return` :( – mihai Sep 10 '13 at 14:07
Why not just `return yourDate.Day < lowestRange.Day || yourDate.Day > highestRange.Day`? I don't know why you're using the bitwise & operator. You should use the boolean || operator as Rotem points out that only one must be true. – Cameron Tinker Sep 10 '13 at 14:07
yes, my original method is what you pasted, but i don't know why stackoverflow doesn't allow me to post it... i'll show the snippet with the error – mihai Sep 10 '13 at 14:08
![stackoverflow validates as error in code][1] [1]: http://i.stack.imgur.com/KF6dn.jpg – mihai Sep 10 '13 at 14:10
Ah, the dreaded can't post answer error. I'm not exactly sure why this happens, but I feel your pain. Also, you're almost correct. If you're going to use the boolean `||` operator, you need to change it to my original comment. – Cameron Tinker Sep 10 '13 at 14:16
cannot post `&&` toghether :( – mihai Sep 10 '13 at 14:25

score 0 · Answer 5 · answered Sep 10 '13 at 14:06

You can use Day property directly to check if your date is within some range using code from other answers.

MSDN says that

Starting with the .NET Framework 2.0, the DateTime structure contains a 64-bit field composed of a private Kind field concatenated with the Ticks field.

Therefore, the most efficient way to compare DateTime instances is to use Ticks property:

DateTime dateToValidate = SomeDate();
DateTime start = SomeRangeStart();
DateTime end = SomeRangeEnd();

return start.Ticks <= dateToValidate.Ticks && dateToValidate.Ticks <= end.Ticks;

Rob van der Veer · Answer 6 · 2013-09-10T14:05:24.330

-1

To properly test if a date (day) is between given numbers, you must use the entire date, or the formula will fail if the date reaches the end of the month.

The example below checks the margin by adding days (or subtracticting days) by using AddDate to greate the boundary date. Then check if the current date is between the boundaries.

var now = DateTime.Now;
if(date.AddDays(-5) < now && now < date.AddDays(5))
{
   return true;
}

edited Sep 10 '13 at 14:05

answered Sep 10 '13 at 13:58

Rob van der Veer

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-1 What does this have to do with anything? – Rotem Sep 10 '13 at 14:01
@Rotern. All you people are quick to downvote, I am trying to explain that just checking the `.Day` is not sufficient, if the date you are trying to test is close to a months start or end. Therefore you must test if the entire date is between to dates. – Rob van der Veer Sep 10 '13 at 14:03
That really wasn't the question. Nowhere does it say anything about `Now`. – Rotem Sep 10 '13 at 14:05
@Rotem the original question is about a date? Otherwise why would OP mention two dates? Anyway, my guess is that OP will eventually find out. – Rob van der Veer Sep 10 '13 at 14:06
The question is about determining if a date falls between two other dates. Not if a date is +-5 days from now. – Rotem Sep 10 '13 at 14:10
I give up. If people don't appreciate me here, i'm off. – Rob van der Veer Sep 10 '13 at 14:11
3

I downvoted an answer I thought was wrong. I gave feedback on that downvote because that is a site guideline. You shouldn't be taking it personally. – Rotem Sep 10 '13 at 14:13
+1, For the idea, I guess the OP would have considered month as well, but since its not specified in the question, its upto OP to clarify. – Habib Sep 10 '13 at 14:31

C#: efficient way to check if datetime.Day within a certain range?

6 Answers6