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DateTime to end of the day C#

I receive a date like 1.01.2022 h:00, m:00, s:00, ms: 00
What is the best approach to get the date at the end of the day, something like: 01.01.2022 h:23, m:59, s:59, ms: 999?
I tried those 2 ways:
var endOfDay = new TimeSpan(0, 23, 59, 59, 999);
time = time.Add(endOfDay);
and
time = time.AddDays(1).AddMilliseconds(-1);

This removes all doubt down to the resolution of a single tick. In the code below, assume that dateAndTime could include a non-zero time component.
dateAndTime.Date.AddDays(1).AddTicks(-1);
This
ensures we are only working with a date that has no time component as our reference point/date
moves us to the next date at midnight
subtracts a single tick, bringing us back to our reference date with a full-resolution time component (you could do milliseconds if you prefer, just know it's less resolution).
While this works, it's generally better to consider an alternate design that doesn't rely on a time component at all (e.g. use a given date at midnight on the next day to act as a virtual end-of-day for the given reference date).

If you want just to print out the range, the action format is opinion based. If you, however, want to check if some time is within or without the day, please do it as (note >= and <)
if (timeOfQuestion >= day.Date && timeOfQuestion < day.Date.AddDays(1)) {
...
}
Using onstructions like endOfDays = time.AddDays(1).AddMilliseconds(-1) is dangerous:
please, note that day.Date.AddMilliseconds(999.5) - double value - should be within the day.

Subtracting an unknown interval from a datetime

I am setting up a system to gather data from a database based on a user inputted start date and end date. The system will gather data averaged over an interval(1 hour, 6 hours, or one day for example). If the user does not input a start or end date I would like the program to set the start date to the current time minus the interval.
I currently have the user inputting the interval in the following format.
1m = 1 minute
1h = 1 hour
12h = 12 hours
3d = 3 days
So these values are not formatted like datetime. I could take the current datetime and subtract it by either minutes, hours, or days depending on the value appended (splitting on the number), but this would mean many if statements. What I would really like is a method to subtract a datetime by an arbitrary value Does anyone have a better solution?

Instead of providing predefined time intervals (that are implemented e. g. via a separate type/enum), it is much easier to let the user freely specify a TimeSpan.
This has two advantages:
The user is not restricted to predefined intervals
You can subtract the TimeSpan directly from your DateTime.Now
If restriction to limited intervals is a requirement, you can implement this in the view/window. But still this should be a TimeSpan.

Comparing time regardless of date

I have an object that has properties currently as DateTime.
The object is marked as valid within a time frame. The default being 00:00:00 to 23:59:59
The user enters the value in the UI and the property is set via:
new DateTime(DateTime.Now.Year,
DateTime.Now.Month,
DateTime.Now.Day,
model.Hours,
model.Minutes,
model.Seconds)
This is then converted to UTC when it hits the database.
Today's date is 29th August 2013. If a colleague in India runs this program it will store the data in the database as 28th August 2013 18:30:00 as they are 5.5 hours ahead of UTC so 29th August 2013 00:00:00 becomes yesterday.
When the logic tries to determine if the object is valid the logic is:
if (DateTime.UtcNow.TimeOfDay > model.MyPropertyFromDB.TimeOfDay)
We are trying to determine if the current time is within a range of 00:00:00 and 23:59:59
This fails as 14:00 (current time) is not greater than 18:30
What would be the best approach to compare just times?
Would storing the values as DateTimeOffSet help, is using ToLocal() ok?
Other considerations are that a user in India is using the app which is hosted in the UK so it needs to be timezone aware.
Thanks

Like others, I'm still unclear on exactly what you are wanting. But clearly, you shouldn't do this:
new DateTime(DateTime.Now.Year,
DateTime.Now.Month,
DateTime.Now.Day,
model.Hours,
model.Minutes,
model.Seconds)
That would be much better as:
DateTime.Today.Add(new TimeSpan(model.Hours, model.Minutes, model.Seconds))
But why are you doing this to begin with? Either of these would give you back the local date. I assume this is going to run on a server, so do you really want the time zone of the server to influence this result? Probably not. Please read: The Case Against DateTime.Now.
If you wanted the UTC date, you could do this:
DateTime.UtcNow.Date.Add(new TimeSpan(model.Hours, model.Minutes, model.Seconds))
That would at least be universally the same regardless of your server's time zone. But still, I don't think this is what you are after.
What's not clear is why is the user only entering the time while you are assigning the current date. If the date is relevant, then shouldn't the user enter it and it would be part of your model?
If the date is not relevant, then why are you storing it? You can use a TimeSpan type for the time value internally. You didn't say what your database is, but let's just guess that it is SQL Server, in which case you could use the time type on the field in the table.
I suppose it's possible that the date is relevant, but you want to control it, while the user takes control of providing the time. If that's the case, then you must know the time zone of the user (or the time zone of whatever the context is if it's not the user). Assuming you had a Windows time zone identifier (see the timezone tag wiki), then you could do something like this:
var tz = TimeZoneInfo.FindSystemTimeZoneById(theTimeZoneId);
var local = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, tz);
var dt = local.Date.Add(new TimeSpan(model.Hours, model.Minutes, model.Seconds));
If you don't have the time zone information, then this wouldn't be possible to solve.
As general advice, you might want to try using Noda Time instead of the built-in stuff. It's much better at helping you figure out this sort of thing. From the main page:
Noda Time is an alternative date and time API for .NET. It helps you to think about your data more clearly, and express operations on that data more precisely.
That appears to be directly the problem you are having here. If you want to clarify some of the questions I asked, I'd be happy to edit my answer and show you exactly how to do this with Noda Time.
Why your question is confusing
We are trying to determine if the current time is within a range of 00:00:00 and 23:59:59
All times are within that range. Well, maybe a value like 23:59:59.1 would be outside of it, but you aren't collecting fractional seconds in your model, so that's irrelevant. But why would you need to validate that? Maybe you are just trying to avoid numbers that aren't valid times at all? Like 99:99:99?
This fails as 14:00 (current time) is not greater than 18:30
Wait - you didn't say anything about comparing one time greater than another. 14:00 and 18:30 are both still in the range you specified.
What would be the best approach to compare just times?
Hard to answer. Are they both UTC times? Is one UTC and one is local? Are they both local? Do you know the time zone of the local times? Are you prepared to deal with ambiguous or invalid local times do to daylight saving time transitions?
Would storing the values as DateTimeOffSet help?
Perhaps, but you haven't given me enough information. It would help only if the date portion is relevant and the you get the correct offsets.
is using ToLocal() ok?
I would argue that no, it's not ok. Local in this context will give you the time zone of the server, which you probably don't want to introduce into your business logic.

So if I understand this correctly you have a time saved in UTC in the database and you are trying to determine whether it falls within a particular time frame? I'm not sure if you want the time frame in local time or UTC so here are both:
DateTime dbTime = model.MyPropertyFromDB;
TimeSpan minTime = new TimeSpan(0, 0, 0);
TimeSpan maxTime = new TimeSpan(23, 59, 59);
if (dbTime.TimeOfDay > minTime && dbTime.TimeOfDay < maxTime)
{
//Within time range (UTC)
}
if (dbTime.ToLocalTime().TimeOfDay > minTime && dbTime.ToLocalTime().TimeOfDay < maxTime)
{
//Within time range (local)
}
Edit: If you want to compare Now to a start and end time from an object in database:
TimeSpan now = DateTime.UtcNow.TimeOfDay;
TimeSpan startDate = model.startDate.TimeOfDay;
TimeSpan endDate = model.endDate.TimeOfDay;
if (now > startDate && now < endDate)
{
//Within time range (UTC)
}

I would say that the methodology being used here is fundamentally flawed and that you need to take a different approach.
new DateTime(DateTime.Now.Year, // Server date
DateTime.Now.Month,
DateTime.Now.Day,
model.Hours, // Local time
model.Minutes,
model.Seconds)
I can't see a way of 'normalising' the input in this way, unless you have a way of reliably knowing exactly which timezone a user is in. Simply, there's no easy way to turn a date built in this way into UTC.
My first question to you is, how is the model being passed from client to server? If you're using javascript/ajax then the solution should be fairly straightforward to solve by constructing the datetime object on the client (which will include their timezone data) and then rely on the browser to convert it to UTC for transit.
If you are using Razor\MVC then you can achieve a similar thing with forms encoding, except that you will need to call ToUTC on the server as the browser won't automatically fix the date for you for this media format.
Both methods require that you build a full datetime object on the client and then submit it, rather than trying to build it from seconds, minutes, hours on the server. You don't need to expose all this to the client of course, as long as the datetime is fully formed at the point of submission.
Once you've got a nice UTC datetime, you can extract just the time if you don't need the rest of it.
Hope this helps.
Pete

Storing a TimeSpan between two DateTimes

I need a way to store and manipulate a date range using C# and storing the data in a SQL database. Is storing two DateTimes the best way to go about this?
For example I need to employees to be able to select the duration they spent working on a specific project by selecting the start date and end date using a DatePicker.
I have the following further requirements:
I need to support half days at start
and/or end of the duration.
I need to be able to calculate the number of
days between the two dates (as a
double where 0.5 is half a day).
I need to be able to calculate the
number of business days between the
two dates (as a double).
The time span needs to be displayed on a
jquery calendar.
The minimum
duration is half a day.
A Date Range of 1/2 Day From 24th May to a full day 27th May:
2011-05-24 12:00:00.000 => 2011-05-28 00:00:00.000
A Date Range of Full Day From 24th May to a 1/2 day 27th May:
2011-05-24 00:00:00.000 => 2011-05-27 12:00:00.000
A Half Day on 24th May:
2011-05-24 12:00:00.000 => 2011-05-25 00:00:00.000
A Full Day on 24th May:
2011-05-24 00:00:00.000 => 2011-05-25 00:00:00.000
Does this representation make sense? Should I rather look at storing a DateTime for the StartDate and a TimeSpan taking into account my requirements?
Edit: also
Does my representation of end date make sense? So that 2nd of may will be saved as '2011-05-03 00:00:00.000' because that is when the duration ends. Bearing this in mind I'll need to subtract a day from the end date when displaying this in a calendar..

I suggest to save the start and end date to your database. The difference can always be calculated.
The critical aspect of date ranges is how to handle the boundaries. You can use a mapper for the start/end date to ensure correct time calculations (Inside/Touching):
// ----------------------------------------------------------------------
public void TimePeriodMapperSample()
{
TimeCalendar timeCalendar = new TimeCalendar();
CultureInfo ci = CultureInfo.InvariantCulture;
DateTime start = new DateTime( 2011, 3, 1, 13, 0, 0 );
DateTime end = new DateTime( 2011, 3, 1, 14, 0, 0 );
Console.WriteLine( "Original start: {0}",
start.ToString( "HH:mm:ss.fffffff", ci ) );
// > Original start: 13:00:00.0000000
Console.WriteLine( "Original end: {0}",
end.ToString( "HH:mm:ss.fffffff", ci ) );
// > Original end: 14:00:00.0000000
Console.WriteLine( "Mapping offset start: {0}", timeCalendar.StartOffset );
// > Mapping offset start: 00:00:00
Console.WriteLine( "Mapping offset end: {0}", timeCalendar.EndOffset );
// > Mapping offset end: -00:00:00.0000001
Console.WriteLine( "Mapped start: {0}",
timeCalendar.MapStart( start ).ToString( "HH:mm:ss.fffffff", ci ) );
// > Mapped start: 13:00:00.0000000
Console.WriteLine( "Mapped end: {0}",
timeCalendar.MapEnd( end ).ToString( "HH:mm:ss.fffffff", ci ) );
// > Mapped end: 13:59:59.9999999
} // TimePeriodMapperSample
Check out the article Time Period Library for .NET (section Calendar Time Periods).

Ideally, you will need two fields anyway:
Store two date/time separately --OR--
Store one date/time and store the time-elapsed
Reviewing your requirements, I would go for two separate date/time fields; and calculate the fulldays/halfdays including (adding/subtracting) holidays.
Keep a separate configuration table to define/configure the max/minimum duration of the day.
Perform any calculations on the day/time, within the query, or alternatively on the UI, upon user actions - if you desire.

Only store start and end dates. Then to calculate no of days worked:
Round(DateDiff(hour, StartDate, EndDate)/24, 2)

To me it seems like storing 2 datetime's makes the most sense.

It really depends on how you intend to use your data. If your second date will never be used outside of calculating the TimeSpan, you should not store it, and store the TimeSpan instead. If you use the end date frequently and only seldom calculate the duration, you should store the 2 datetimes.
You can even consider to store the three values if you use them frequently and the increase in memory space is not a problem.

I believe two DateTime Fields along with checkboxes corresponding to Start and End date to indicate whether its Half or Full day would be sufficient for you. based on the Checkbox state you can manipulate the time component to suit your needs. You will just have to store the Start and End DateTime values which would adhere to the requirements you posted.

Building a Datetime Object for SQL database insert

I'm working on a small web form that requires the user to input (among other things), the scheduled backup time of whatever server they're adding to the system. The problem is, I'm struggling to find out the best way to take the user input and build a DateTime object (which is what the database requires).
I only really care about the Day of Week, Time of Day (12 or 24 hour clock).
I thought about just creating an empty DateTime object and then just adding my input values from the user, but you can only get, not set, the day of week, time of day, etc.
I've been looking at the Calender asp control, which would work for the day of the week selection, but I can't seem to find any support of time of day.
Thanks.

I don't think you want to use a DateTime for a recurring event such as a backup. A DateTime is useful for storing a particular date and time, but not a "template" for a recurring event. Instead I'd use separate columns to store the day of week value (0-6) and time of date (minutes after midnight) for the event.

If you going to use datepicker here is one great sample for adding JQuery date picker using C#. That helped me including in my project evrn if I did know anything abaut JQuery and java sripts at all.

DateTime is a immutable value type. You cannot set anything on it.
Assumed that you stick with DateTime on the DB and you don't want to use a DateTimePicker control.
You have to specify how the day of week and the time should be represented in the DateTime. You can start with DateTime.MinValue, the 1.1.0001, 12:00 at midnight, and add the day of week and the time. unfortunately, a regular DateTime field in a SqlServer 2005 is not able to store this date. So lets move it to the year 2000. The 1.1.2000 was a Saturday. You could calculate the DateTime like this:
int dayOfWeek; // 0 = mon, 6 = son
DateTime time;
DateTime scheduleTime = new DateTime(2000, 1, (dayOfWeek + 2) % 6 + 1)
+ time.TimeOfDay;
But honestly, I wouldn't do it. It smells. I just answered your question. Listen to tvanfosson. He said everything that needs to be said.