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.
Related
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.
When I search about maximum time. people always answering that from VS debugger. which is 23:59:59.9999999
As I need 12 AM in 24 formats. I guess it will be 00:00:00 but...
C# .NET assume the following:
var xx = DateTime.MaxValue.ToString("HH:mm:ss.fffffff");
When debugging previous it will print 23:59:59.9999999
What should I use? does it matter? what's the difference?
Should use 00:00:00 ? or 23:59:59.9999999 Specially when
saving Time in SQL-Server.
The big problem or I mean un-good behavior for end-user when you convert 24 formats to 12 Hour format via hh:mm:ss it will show 11:59:59 PM it will be ugly isn't it? it should be 12:00:00 AM.
After All, Obsidian Age answered this well depending on the use case.
It depends on perspective:
var xx = DateTime.MaxValue.ToString("HH:mm:ss.fffffff");
var xy = DateTime.MinValue.ToString("HH:mm:ss.fffffff");
Gives
23:59:59.9999999
00:00:00.0000000
So, one is the end of the day and the other is the beginning of the day.
There's an interesting novel called 'The time between midnight'
DateTime.MaxValue is exactly that - the maximum value that DateTime can represent; that is to say, the 'last' point in a day. Conversely, the .Date property makes use of 00:00:00 by default, as it has no notion of time (unless specified).
If you have an event that occurs at exactly midnight, I would recommend storing it as 00:00:00, as the event occurs at midnight, and you want to accurately represent that.
Ultimately, it really depends on your desired use case as to which one you want to use. Do you want to state that the event occurs on day 1's evening, or day 2's beginning? That is what it boils down to, although in the vast majority of cases such a delineation makes no difference. In this case you would want to opt for both the accuracy and 'ease' of 00:00:00.
programmatically speaking, you can do both. the only difference between them (in code) is this :
// using 00:00:00 will require you to add 1 day to the end date in order to count as full day
if(time >= "2019-12-03 00:00:00" && time < "2019-12-04 00:00:00")
//using 23:59:59 will not require you to add 1 day to the end date.
if(time >= "2019-12-03 00:00:00" && time <= "2019-12-03 23:59:59")
so, basically, if you use 23:59:59 there is a one second off the grid, if any record has been stored in this second, it'll not be included in the results. while the second one will include it.
Which one to use ? surely the 00:00:00 if you want to be more precise, however, I've not seen any difference in the results in my projects as I've used both of them in different projects. But I'm sure there are some projects needs to include every micro second as this microsecond could change the result's curve (such as analytics or deep learning ..etc).
In SQL Server, don't save the time as string, save it with the correct datatype (DateTime, TimeSpan ..etc). SQL Server will reads the time perfectly fine when you pass a correspond time datatype from your application.
A few things:
The maximum value that a DateTime in C# can represent is 9999-12-31 23:59:59.9999999. In SQL Server, this corresponds to a datetime2, which has the same maximum value.
The time type in SQL Server also has a maximum value of 23:59:59.9999999 (though note that a C# TimeSpan can be much larger because it primarily represents duration instead of time of day).
If you are storing just a time range using the time type, you'll need that 23:59:59.9999999 value for the end of the day. You can get this quickly in C# with DateTime.MaxValue.TimeOfDay. Indeed it will be one tick less than a true 24:00.
There are 7 decimals of nines because that is the precision offered by the data type. If you choose a lower precision, there is some small (but not impossible) chance that a given value could fall after it. Thus when you use this technique, always align the nines with the full precision of the data type. (Don't just subtract one second or one millisecond.)
When calculating the difference of a datetime range such as 2020-01-01 00:00 to 2020-01-01 01:00, one can simply subtract the two values to get the result (1 hour in this case). However, when using 23:59:59.99999999, one has to account for the missing tick. This can get messy, and such there is a significant advantage to using 00:00 instead.
As you pointed out, when displaying 23:59:59.9999999 to an end user, you may have to write your own logic to format it as 24:00 or as "end of day", etc.
When comparing datetime ranges, you'll want to use a different operator for the end comparison:
If you use 23:59:59.9999999, use a fully-inclusive range comparison: a <= now && b >= now
If you use 00:00, use a half-open range comparison - inclusive at the start, exclusive at the end: a <= now && b > now
When comparing time-only ranges (i.e. timspan types), the same logic applies, but one also has to consider time ranges that span over midnight:
If you use 23:59:59.9999999:
if (a < b)
result = a <= now && b >= now;
else
result = a <= now || b >= now;
If you use 00:00:
if (a < b)
result = a <= now && b > now;
else
result = a <= now || b > now;
In summary, it is generally simpler to work with 00:00 values instead of 23:59:59.9999999 values, and thus you should prefer 00:00. If you find the need to use 23:59:59.9999999, you should be aware of the coding changes required.
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.
I have a rather interesting problem at the minute where i want to return the actual hour values between two times. I dont mind if this is either in c# or mysql but i'm not sure what way to go about it.
Eg Time 1= 13:00 & Time 2= 18:10
i would like to return 13:00,14:00,15:00,16:00,17:00,18:00
There is plenty around for calculating the hour count between two times and i know i can use that integer value and increment my base hour as below but i was wondering if there was a cleaner way?
Mysql
timediff('2014-04-01 18:10:00', '2014-04-01 13:00:00' )
returns 05:10:00
hour('2014-04-01 13:00:00')
returns 13
increment the 13 by the hour value
seems long winded :(
In C# to enumerate all (full) hours from start to end:
public static IEnumerable<DateTime> Hours(DateTime start, DateTime end)
{
start -= TimeSpan.FromMinutes(start.TimeOfDay.TotalMinutes);
end -= TimeSpan.FromMinutes(end.TimeOfDay.TotalMinutes);
return Enumerable.Range(0, (int)Math.Ceiling((end - start).TotalHours))
.Select(x => begin + TimeSpan.FromHours(x));
}
First we remove minutes from interval boundaries, we need whole hours only (so 10:30 and 11:10 will result in two hours, not just the difference between them). Then we create an enumeration from zero to number of whole hours, we'll use it to create offsets from beginning. I keep start DateTime using calculated TimeSpan as offset to keep track of date changes (for example if interval boundary is across two or more days).
If, for example, start is 2014/04/01 10:25 and end is 2014/04/01 13:20 then you'll get:
2014/04/01 10:00
2014/04/01 11:00
2014/04/01 12:00
2014/04/01 13:00
To get just time part change return type to IEnumerable<TimeSpan> and last Select() to:
.Select(x => (begin + TimeSpan.FromHours(x)).TimeOfDay);
In SQL it can be done but it's little bit more tricky because you need a working table with a sequence of integers. Please note following code is untested.
First you need to calculate that difference:
CEIL(TIMESTAMPDIFF(MINUTE, startDate, endDate) / 60)
Now you can use a working table filled with numbers for offsets:
Value
-----
0
1
2
3
...
With this:
SELECT
DATE_ADD(startDate, INTERVAL Value HOUR)
FROM
NumericTable
WHERE
Value <= CEIL(TIMESTAMPDIFF(MINUTE, startDate, endDate) / 60)
In both cases (C# and SQL) you may replace output DateTime/Date with a TimeSpan/TIME object).
I recommend working with DateTime and TimeSpan classes. You can use this:
double HoursBetween(DateTime t1, DateTime t2)
{
return (t2 - t1).TotalHours;
}
You may want to apply some rounding if you need int return type.
What is happening is that the - operator for two DateTime objects is defined so a TimeSpan object is created which holds the time difference. TotalHours simply returns the TimeSpan value expressed in whole and fractional hours.
I am working on an application with train schedules, where the first train leaves at 0400 while the last train leaves at 0200. The users of this application therefore deal with days starting at 0300 and ending at 0300. In other words, when they say "The Wednesday-train at 0200" they really mean "The train that leaves on Thursday at 0200".
Our application needs to store all of the trains leaving on (for example) Wednesday, which means it should not include the trains that leave before 0300 but it should include the trains that leave the next day until 0300.
How would I represent this in application without going mad? And how should this be stored in a database for easy querying?
I would store the actual date/time value. Then for querying, to search for "anything on Wednesday" you'd go from Wednesday 0400 (inclusive) to Thursday 0400 (exclusive).
In terms of display, you'd probably be best taking the date, and subtracting a day if the time is earlier than some cutoff:
private static readonly LocalTime CutOff = new LocalTime(4, 0, 0);
...
LocalDate date = dateTime.Date;
if (dateTime.TimeOfDay < CutOff)
{
date = date.PlusDays(-1);
}
var dayOfWeek = date.IsoDayOfWeek;
I would try to avoid using the date on its own as far as possible, to avoid going mad. Any date/time will be unambiguous.