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How can I specify the latest time of day with DateTime
I need to compare a date range and am missing rows who's date is the upper comparison date but the time is higher than midnight. Is there a way to set the upper comparison's time to 23:59:59?
This is a possible solution:
yourDateTime.Date.AddHours(23).AddMinutes(59).AddSeconds(59);
Why not have the upper comparison being midnight on the day after the last one you're interested in, and then use that with an exclusive comparison?
DateTime upperExclusive = lastInclusive.Date.AddDays(1);
if (dateInclusive >= date && date < upperExclusive)
{
....
}
This feels like a cleaner solution than finding the last second of the day - aside from anything else, you'd still be missing values of 23:59:59.500 etc with your current scheme.
Obligatory plug: I'm not a huge fan of the BCL date/time API. You may want to keep tabs on Noda Time - a port of Joda Time to .NET.
If your doing a compare why don't you compare against less that the start of the next day?
Eg. if it was a Linq query:
someList.Where(x => (currentDaysDate <= x.ItemDate ) && (x.ItemDate < nextDaysDate))
Create an EndOfDay extension method
public static DateTime EndOfDay (this DateTime d)
{
return DateTime.Parse(d.ToShortDateString().Trim() + " 23:59:59");
}
Just use one day later than the upper comparison, and < on the upper side instead of <=. That way, you can get times that are even later (fraction of a second) than the one you specified.
Alternatively, compare using the DateTime.Date property instead of the DateTime directly. This will "strip off" the time portion, so your dates in the search will automatically be treated as midnight.
If you are not worried about the time at all, you can use the Date Property of DateTime, which returns just the date part (with the time set to 00:00:0000)
if(MyDate.Date >= StartDate.Date && MyDate.Date <= EndDate.Date)
{
//Code here
}
Yes, this DateTime constructor - http://msdn.microsoft.com/en-us/library/272ba130.aspx
allows you to specify the date as well as hours, minutes and seconds.
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Showing Difference between two datetime values in hours
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Found what I needed right after I posted (of course). Thank you for the help. I wasn't understanding TimeSpan and didn't realize I could simply tack .TotalHours to the end of my TimeSpan variable to get what I needed.
Please explain like I'm 5 years old.
I have two DateTimePicker objects with a custom format of HH:mm so that only military time is entered. Date is irrelevant. One picker is for the start time and the other picker is for the end time.
I need to be able to subtract the start time from the end time in order to get a total length of time in hours between them.
I then need this length of time converted to an integer I suppose? So that I can later use an if statement to see if it is equal to or above a certain number.
I know that DateTime can use the > < and other operators, so that's what I'd like to use.
However when I try to create a variable like so:
var timeLength = endTime.Value - startTime.Value;
It tells me its a TimeSpan variable.
I tried to make a DateTime variable so I could use the > < and other operators later:
DateTime timeLength = endTime.Value - startTime.Value;
And I get red squigglies
"Cannot implicitly convert type 'System.TimeSpan' to 'System.DateTime'
Well okay VS, I don't want a TimeSpan variable. At least I don't think I do?
Anyway, obviously this means I can't later user the shiftLength variable to compare to things, so that's not working.
I tried to do it straight in my if statement:
if (endTime.Value - startTime.Value <= 12)
Operator '<=' cannot be applied to operands of type 'TimeSpan' and
'int'
Alright. Fine. So.
1) Why is it calling this a TimeSpan variable. I'm trying to look into TimeSpan properties and it's confusing the heck out of me. Do I need to use TimeSpan to accomplish what I'm trying to do? and if not..
2) What's the simplest way to subtract my DateTimePicker endTime.Value from my startTime.Value to be able to compare it to an integer with < > = operators?
Use the TotalMinutes (TotalHours, TotalSeconds etc) property of the TimeSpan:
if ((endTime.Value - startTime.Value).TotalHours <= 12)
{
....
}
Ref.: TimeSpan
To provide a TRIAL period to my application when the user first runs the application I save the FirstRunTime like this:
string sFirstRunDate = DateTime.Today.ToShortDateString();
saveInfo.saveFirstRun(sFirstRunDate ); // saves as a string to a text file
Now everytime I run the application I want to see if it has been more then 60 days and if so terminate (60-day trial only). How can I do that compare?
string sFirstRunDate = saveInfo.getFirstRun(); // returns the string I saved earlier
DateTime dtFirstRunDate = DateTime.Parse(sFirstRunDate); // makes it a DateTime
DateTime now = DateTime.Today.ToShortDateString(); // why am I doing this?
So how can I take the two dates and compare them to see if it has been more then 60 days or not?
Thanks,
The following should do it:
var elapsed = DateTime.Today.Subtract(dtFirstRunDate);
if (elapsed.TotalDays > 60)
{
// trial expired
}
The advantage of this is when the trial hasn't expired you can tell them how far they are into their trial (using elapsed.TotalDays).
TimeSpan t = DateTime.Now.Subtract(dtFirstRunDate);
if (t.Days > 60)
{
//do something
}
Try
if(DateTime.Parse(sFirstRunDate).AddDays(60) < DateTime.Now) {
// trial has expired
}
This just takes the first run, adds 60 days to it, if the current time is greater than the time first run + 60 days, the trial is over.
All other answers are technically going to work for you, but they are wrong on a larger scale. Please read further.
// why am I doing this?
This tells me that you do not quite grasp the concepts you're trying to apply. Let's go one by one.
string sFirstRunDate = DateTime.Today.ToShortDateString();
There are two problems with that. First the DateTime.Today returns the local date/time. Never ever use local date/time for any kind of calculations because local time is not consistent. Daylight changes, travel through time zones, all affect the local time that is returned by this property. What you should use instead is DateTime.UtcNow.Date to get the current UTC time which is the global clock not affected by any of the aforementioned problems.
Second problem is the ToShortDateString method. It converts the date/time using current culture. Did you know that in other parts of the world, the date is reported as 'DD/MM/YYYY', or 'YYYY-MM-DD'? What will happen if the user changes current locale? To avoid those problems you should use the ToString(CultureInfo.InvariantCulture) method.
The correct code to serialize the first run date is
string sFirstRunDate = DateTime.UtcNow.Date.ToString(CultureInfo.InvariantCulture);
DateTime now = DateTime.Today.ToShortDateString(); // why am I doing this?
To calculate the difference between two dates, first you need to acquire those two dates. The first one would be the saved first run date, and the second would be today. You did the first part by deserializing the first run date into DateTime structure. For the second part you just need the current date, you don't need to serialize it into string. So
DateTime today = DateTime.UtcNow.Date;
Now that you have two dates, you have an array of options on how to actually get the difference. Any of the other answers do that part just fine. I personally like Timothy Walters' answer as it has a nice side effect of giving your the days left for trial. It will look like:
DateTime dtFirstRunDate = DateTime.Parse(saveInfo.getFirstRun());
DateTime today = DateTime.UtcNow.Date;
var elapsed = today.Subtract(dtFirstRunDate);
if (elapsed.TotalDays > 60)
{
// trial expired
}
I need to compare whether date is less than 3 months old.
I will get installation date:
DateTime installdate=DateTime.Parse("1/5/2012 8:12:14 PM");
if ((installdate<DateTime.Now.AddMonths(-3)))
{
// do something
}
Is this the best way to compare the dates?
Thanks.
A few things to think about:
"Is date x earlier than 3 months before today" isn't the same as "today is more than 3 months later than date x"; you'll need to make sure you have the exact semantics you want.
Consider what you want to do with the time component - are you interested in dates or dates and times? (Would you expect the condition evaluation to change based on the current time of day?)
Consider time zones: are you interested in "today in the system's current time zone" or some fixed time zone?
Depending on the source of the text data, you should possibly use DateTime.TryParse and you should possibly use DateTime.ParseExact or DateTime.TryParseExact, passing in the expected format (and culture)
Basically, there are various corner cases around date and time behaviour - you should explicitly think about all of these things (some of which are forced upon you if you use Noda Time instead of DateTime, btw :)
Regarding the first point, if the idea is that you get a trial period of three months from the installation date (or something similar), that suggests you should be adding three months to that instead.
I'd also change the variable name and get rid of the redundant parentheses, by the way:
DateTime installationDate = DateTime.Parse("1/5/2012 8:12:14 PM");
DateTime trialPeriodEnd = installationDate.AddMonths(3);
if (trialPeriodEnd > DateTime.Now)
{
// do something
}
Assuming you're storing the installation date yourself somewhere, I would try to store it in some form which is less ambiguous - possibly even storing just a "ticks" value instead of a string. But assuming you are storing it yourself, you shouldn't need to use TryParse - it makes sense to go "bang" if you can't parse the value. I'd use ParseExact, probably with a standard format specifier of "o" (round trip).
DateTime installdate ;
if (DateTime.TryParse("1/5/2012 8:12:14 PM", out installdate))
{
if ((installdate < DateTime.Now.AddMonths(-3))) { }
}
Tryparse is used so as to validate if the date passed in the parameter is valid or invalid
In C# if I want to parse a datetime, but some times I just have either a date and not a time component or no date but a time component, how would I do this? Usually when you leave out the time component, it automatically assumes that the time is 12:00AM. But I don't want this. If the time component is missing then I just want the DateTime to store a date only and the leave the time component off.
The value of a DateTime internally is just an UInt64 (ulong in C#) that stores the number of ticks since some date in the past, so whether you like it or not, the time component will always be there.
If you only need to display certain parts, just use any of the format strings (examples are for "en-us" culture):
DateTime.Now.ToString("d"); // 5/26/2009
DateTime.Now.ToString("t"); // 4:56 PM
The complete reference: http://msdn.microsoft.com/en-us/library/az4se3k1.aspx
It's not possible to have a DateTime without a time component. You could store a boolean flag along with it in a struct to store data about existence of that component. However, there's no way to use the automatic parsing routine to distinguish between a DateTime string with a time specified as 12:00 PM and a nonexistent one.
If it really bugs you you can always create a wrapper class that can hide the time portions of the datetime class.
No you will have the time component no matter what. The best you can do is access the Date property on your DateTime object if you really have to.
http://msdn.microsoft.com/en-us/library/system.datetime.date.aspx
DateTime by definition stores a date and a time such that it cannot just represent one of them without representing the other. If you only want the date (or only the time), parse out the information you need and discard the rest of it.
As mentioned before DateTime will always have a Date and a Time part of it if you only want a single part use the way described by the others
DateTime date = DateTime.Parse("2009-11-30);
date.Year; = 2009
date.Month; = 11
date.Day; = 30
date.Hour; = 0
and so on
The thing you must be aware is that all of these methods will only return an integer.
If you want to know all the possible ways to parse a string John Sheehan has put together a great Cheat Sheet wit all possible ways to parse and manipulate dates, and other strings for that matter.
You could have a class that stores a DateTime and determines if the time was ever set or if just the date was set and return values accordingly.
Use
DateTime date = new DateTime();
date = DateTime.Parse("1/1/2001");
to set the date, then use
date.ToShortDateString();
or
date.Year;
date.Month;
date.Day;
to get what you need. Hope that helps!
A DateTime object is always stores a date + a time, not just one. You can always choose to work only with the date part, i.e. only use properties like Year, Month, DayOfWeek. But underneath there will aways be some stored time.
It is very dangerous to assume that the date portion of a DateTime is necessarily the date you are expecting. As pointed-out, DateTime always includes and considers the time aspect, even when you don't see it.
This is a big problem when you have data stored in different time-zones (and particularly if knowledge of that offset is not also kept, because it is assumed that what is being stored is a Date, not a date-with-time).
You may store a birthdate as '01/01/2000 00:00:00' during Summer-Time, which then is stored in UCT as '31/12/1999 23:00:00'. When you then read that birth-date later, the date portion is now a day early.
Best to create your own type. Strange that Microsoft didn't think it worth having a Date type.
I have two datetimes, one from a timestamp, and another I'm generating in code. I need to test their equality, and would love to do it without too many expressions. Here's an example of my two dates:
DateTime expireTimeStampUTC =
DateTime.Parse(UTCValueFromDatabase));
DateTime expectedExpireTime =
DateTime.UtcNow.AddHours(NumberOfExpectedHoursInConfig);
This is too high precision of a test:
if (expireTimeStampUTC.Equals(expectedExpireTime)){}
I don't care if they're exact to the second, just the hour.
Could it possibly be the best solution to do something compound like this:
if (expireTimeStampUTC.Date.Equals(expectedExpireTime.Date))
{
if (!expireTimeStampUTC.Hour.Equals(expectedExpireTime.Hour))
{
pass = false;
}
}
I'm not the most experienced with C#... is there some elegent way to do this?
If the problem you are having is because of them is a database type, you could convert to that type and compare there, we lose/gain about a millisecond converting to SQLDateTimes on roughly 1/3 of DB saves.
If not, compare the unit you actually care about:
DateTime dt1 = DateTime.UtcNow;
DateTime dt2 = DateTime.UtcNow.AddMinutes(59); // or 1 or 61 for test values;
// if the dates are in the same hour (12:10 == 12:50, 1:58 != 2:02)
if(dt1.Hour == dt2.Hour) // result
or if you care that they are within an hour time span
// if the dates are within one hour of each other (1:58 == 2:02, 3:30 != 4:45)
if((dt1 - dt2).Duration() < TimeSpan.FromHours(1)) // result
Here subtracting dates generates a time span, the duration is the 'absolute value' and then we create the limit explicitly from a unit we care about (FromHours) and compare.
The last line is as clean as I can think to do equality within a particular time span.
How about finding the difference between the two hours, and seeing if it's below a certain threshold (say 3600 seconds for an hour)?
var diff = expireTimeStamp.Subtract(expectedExpireTime).TotalSeconds;
pass = Math.Abs(diff) < 3600;
Subtract them. Check whether the resulting TimeSpan is within a certain maximum range.
Construct new DateTime objects and compare them. In C#, there's very little penalty for constructing "throwaway" objects in this way.
I experienced the problem when trying to write unit tests which committed then retrieved business objects. I was trying to use the "StartTime" property of my object to ensure the object could be retrieved and encountered this problem. The "StartTime" value committed in the database lost 6 digits of precision in the Ticks value!
Here's how I rewrote my test condition so my test would perform correctly and pass. Relevant line is second-to-last line of block.
DateTime start = DateTime.Now;
NewEventInfo testEvent1 = FakeEvent("test01action", start); //plus other params for testing
mServiceClient.AddEvent(testEvent1);
EventInfo[] eventInfos = null; //code to get back events within time window
Assert.IsNotEmpty(eventInfos);
Assert.GreaterOrEqual(eventInfos.Length, 1);
EventInfo resultEvent1 = eventInfos.FirstOrDefault(e =>
e.Action == "test01action" &&
Math.Abs(e.StartTime.Subtract(testEvent1.StartTime).TotalMilliseconds) < 1000); //checks dates are within 1 sec
Assert.IsNotNull(resultEvent1);
This way I could be sure the object was the one committed by the unit test, as the EventInfo.StartTime property only uses date times with precision of 1 second.
EDIT: Added Math.Abs(around DateTime diff) to ensure absolute value being compared to 1000.