How can I convert a number between 1 and 7 into a DateTime object in C# which represents the day of the week? The numbers are coming from a XML file which I am parsing. I am retrieving each instance of a field containing a number between 1 and 7 which represents a day of the week between Sunday and Saturday.
I would assume casting to a DayOfWeek object would give you a day of the week
DayOfWeek day = (DayOfWeek)myInt;
As far as a DateTime object goes, the object represents a specific day, not necessarily a random day of the week. You may try adding a # of days to a specific date if this is what you're trying to achieve.
http://msdn.microsoft.com/en-us/library/system.dayofweek.aspx
In order to get a DateTime, you'd need a specific range of dates that you want the weekday to fall under (since a DateTime is a specific date and time, and a weekday isn't).
There is a DayOfWeek enumeration (whose values actually range from 0-6). If all you need is something to represent the day of the week, then you should be able to cast your int to a DayOfWeek like..
DayOfWeek myDay = (DayOfWeek)yourInt;
If you need an actual DateTime, you'll need a start date. You could then do...
DateTime myDate = startDate.AddDays(
(int)startDate.DayOfWeek >= yourInt ?
(int)startDate.DayOfWeek - yourInt :
(int)startDate.DayOfWeek - yourInt + 7);
This will give you a DateTime for the next occuring instance of the day of the week you're describing.
DayOfWeek.Sunday is zero, so you could start with an arbitrary fixed date that you know to be Sunday, and add a value between 0 and 6:
public DateTime GetDayOfWeek(int dayOfWeek)
{
if (dayOfWeek < 0 || dayOfWeek > 6) throw new ArgumentOutOfRangeException(...);
// 4 January 2009 was a Sunday
return new DateTime(2009,1,4).AddDays(dayOfWeek);
}
I'm not sure why you would want this though.
If you only want it to get a localized version of the day of the week as in:
GetDayOfWeek(3).ToString("dddd"); // Gets name of day of week for current culture
an alternative would be to use DateTimeFormatInfo.DayNames or DateTimeFormatInfo.AbbreviatedDayNames for the culture you want.
A DateTime instance represents alway a complete date and cannot only represent a day of the week. If the actual date does not matter, take any monday (assuming 0 represents monday) and just add the number of the day.
Int32 dayOfWeek = 3;
// date represents a thursday since 2009/04/20 is a monday
DateTime date = new DateTime(2009, 04, 20).AddDays(dayOfWeek);
Else I agree with Adam Robinson's answer - if you just want to hold the day of a week, stick with the DayOfWeek enum (zero is sunday) instead of using an integer.
Related
I have problem in finding the date using day of the week.
For example : i have past date lets say,
Date date= Convert.TodateTime("01/08/2013");
08th Jan 2013 th Day of the week is Tuesday.
Now i want current week's tuesday's date. How i can do it.
Note : The past date is dynamic. It will change in every loop.
You can use the enumeration DayOfWeek
The DayOfWeek enumeration represents the day of the week in calendars
that have seven days per week. The value of the constants in this
enumeration ranges from DayOfWeek.Sunday to DayOfWeek.Saturday. If
cast to an integer, its value ranges from zero (which indicates
DayOfWeek.Sunday) to six (which indicates DayOfWeek.Saturday).
We can use the conversion to integer to calculate the difference from the current date of the same week day
DateTime dtOld = new DateTime(2013,1,8);
int num = (int)dtOld.DayOfWeek;
int num2 = (int)DateTime.Today.DayOfWeek;
DateTime result = DateTime.Today.AddDays(num - num2);
This also seems appropriate to create an extension method
public static class DateTimeExtensions
{
public static DateTime EquivalentWeekDay(this DateTime dtOld)
{
int num = (int)dtOld.DayOfWeek;
int num2 = (int)DateTime.Today.DayOfWeek;
return DateTime.Today.AddDays(num - num2);
}
}
and now you could call it with
DateTime weekDay = Convert.ToDateTime("01/08/2013").EquivalentWeekDay();
I may be a bit late to the party, but my solution is very similar:
DateTime.Today.AddDays(-(int)(DateTime.Today.DayOfWeek - DayOfWeek.Tuesday));
This will get the Tuesday of the current week, where finding Tuesday is the primary goal (I may have misunderstood the question).
You can use this....
public static void Main()
{
//current date
DateTime dt = DateTime.UtcNow.AddHours(6);
//you can use it custom date
var cmYear = new DateTime(dt.Year, dt.Month, dt.Day);
//here 2 is the day value of the week in a date
var customDateWeek = cmYear.AddDays(-2);
Console.WriteLine(dt);
Console.WriteLine(cmYear);
Console.WriteLine("Date: " + customDateWeek);
Console.WriteLine();
Console.ReadKey();
}
I want to know the number of days from january 1st to today.
If today is January 10th, then numOfDays=10, if today is February 1st then numOfDays=32.
How can I get the total no of days? Thank you
You can use DateTime's DayOfYear property.
int dayOfYear = DateTime.Now.DayOfYear;
DateTime.DayOfYear is exactly what you want.
To find out the day of year for today:
var days = DateTime.Today.DayOfYear;
This should give you what you are looking for:
int currDayOfYear = DateTime.Now.DayOfYear;
This shows how to do it. Step by step, use DateTime.Now to get a DateTime object representing the current date/time. Then use the DateTime.DayOfYear property.
http://msdn.microsoft.com/en-us/library/system.datetime.dayofyear.aspx
public int DayOfYear { get; }
Property Value
Type: System.Int32
The day of the year, expressed as a value between 1 and 366.
Datetime.Now explained:
http://msdn.microsoft.com/en-us/library/system.datetime.now.aspx
Is There any built in function in c# to compare Compare today's datetime to match like: (First, second, third, fourth, fifth) weekday(mon, tuesday ect.) of current month
or can any one please provide the custom solution for the same.
Regards
Well, you can easily find out whether the day matches:
// Note: consider time zones...
DateTime today = DateTime.Today;
if (today.DayOfWeek == DayOfWeek.Monday)
{
...
}
and you know that the first occurrence of each day of the week will be in the range 1-7, the second will be in the range 8-14 etc. So:
// Check if it's the second Friday of the month...
int targetOccurrence = 2;
DayOfWeek targetDay = DayOfWeek.Friday;
DateTime today = DateTime.Today;
if (today.DayOfWeek == targetDay &&
(today.Day + 6) / 7 == targetOccurrence)
{
// Yes, it's the second Friday
}
If you want to find out whether it's before or after the second Friday of the month, that's slightly harder. Not impossible by any means, but more fiddly.
You can use
DateTime.Now.DayOfWeek
To fetch the current day of week:
DayOfWeek dToday = DateTime.Now.DayOfWeek;
int iDay = dToday.GetHashCode(); // a number between 0-6 representing
// the days in the week
string sDayName = dToday.ToString(); // can be either Sunday, Monday .. Satruday
Use the DateTime.DayOfWeek property.
e.g.
if (DateTime.Now.DayOfWeek == DayOfWeek.Monday)
{
Console.WriteLine("Someone's got a case of the Mondays!");
}
I have an int representing a number of Gregorian days from Year Zero (thanks, Erlang). How do I convert this to a DateTime object? I can't create a DateTime(0,0,0), and Convert.DateTime(int) throws an invalid cast.
If you have a number, and you know the date that it represents (from Erlang), you can calculate the offset from any date you choose. Preferred is a base date in the zone that the results will be in, this will minimize calender conversion effects. (The Gregorian calendar is valid from about 1600).
If you know that offset, you can use the choosen date as the base for future calculations.
Example:
I want my offset date to be: 1/1/2000. This will be the date that I calculcate from.
I know number 37892 from erlang is actually 1/1/1970 (this is an example).
Then I can calculate the offset:
var myBaseDate = new DateTime(2000,1,1);
var exampleNrOfDays = 37892;
var exampleDate = new DateTime(1970,1,1);
var offset = exampleDate - myBaseDate;
var offsetInDays = exampleNrOfDays - (int)offset.TotalDays;
// Now I can calculate
var daysFromErlang = 30000; // <= example
var theDate = myBaseDate.AddDays(daysFromErlang - offsetInDays);
This shows how to calculate number of days from a given date. http://dotnetperls.com/datetime-elapsed
if day zero is 0/0/0 then it is 365+30+1 day before DateTime.Min which is 1/1/1. So you can subtract days from year zero by 365+30+1 and add to DateTime.Min
Now Month 1 is January which is 31 days but what is Month 0? I assumed it is 30 days.
With 0, you probably mean 0:00 on the 1st of January, year 1. There is no year 0 in the gregorian calendar as far as i know.
If the above is right, you can just do
DateTime date = new DateTime();
date.AddDays(numberOfDays);
because the default constructor 'DateTime()' returns the "zero" DateTime object.
See the DateTime reference for more informations.
I am not sure if you are aware of this, but there is a Calendar object in System.Globalization. Not only that but there is a GregorianCalendar object as well.
so try this:
GregorianCalendar calendar = new GregorianCalendar();
DateTime minSupportedDateTime = calendar.MinSupportedDateTime;
//which is the first moment of January 1, 0001 C.E.
DateTime myDate = minSupportedDateTime.AddDays(55000);
//this is when you add the number of days you have.
Thanks,
Bleepzter
PS. Don't forget to mark my answer if it has helped you solve your problem! Thanks.
So I have an application that needs to get a date focus so it can run appropriately. Given a particular date to focus on it needs to know what week it is in. I'm calculating weeks based on Monday dates. And I'm wondering if my focus on Mondays is excessive.
public static DateTime PreviousMonday(this DateTime dt)
{
var dateDayOfWeek = (int)dt.DayOfWeek;
if (dateDayOfWeek==0)
{
dateDayOfWeek = dateDayOfWeek + 7;
}
var alterNumber = dateDayOfWeek - ((dateDayOfWeek*2)-1);
return dt.AddDays(alterNumber);
}
/// <summary>
/// Personal tax week starts on the first Monday after the week with 6th April in unless 6th April is a Monday in
/// which case that starts the first week. In a leap year this means you can have a week 53 which due to the mod 4 approach of calculating
/// flexi week means you get a 5 week flexi period.
/// As such this method forces the weeks into the range 1 - 52 by finding the week number for the week containing 6th April and
/// the number for the current week. Treating the 6th April week as week 1 and using the difference to calculate the tax week.
/// </summary>
public static int GetTaxWeek(this DateTime dt)
{
var startTaxYear = GetActualWeekNumber(new DateTime(DateTime.Now.Year, 4, 6));
var thisWeekNumber = GetActualWeekNumber(dt);
var difference = thisWeekNumber - startTaxYear;
return difference < 0 ? 53 + difference : difference + 1;
}
private static int GetActualWeekNumber(DateTime dt)
{
var ci = System.Threading.Thread.CurrentThread.CurrentCulture;
var cal = ci.Calendar;
var calWeekRule = ci.DateTimeFormat.CalendarWeekRule;
var fDoW = ci.DateTimeFormat.FirstDayOfWeek;
return cal.GetWeekOfYear(dt, calWeekRule, fDoW);
}
public static int PeriodWeek(this DateTime dt)
{
var rawPeriodWeek = GetTaxWeek(dt) % 4;
return rawPeriodWeek == 3 ? 1 : rawPeriodWeek + 2;
}
}
The system runs a rolling 4 week schedule starting in the first tax week and needs to behave differently depending on where in the schedule it is. So you can see...
Get a date from a user (say userDate)
Call userDate=userDate.PreviousMonday();
to get to the Monday of the week
given - where Sunday is the week end
Call userDate.PeriodWeek(); and get
the Period you are in from 1 to 4.
GetTaxWeek is public because it is used elsewhere... I also replace the date as it is used more than once and I don't want to have to remember to change it more than once.
Can I see the wood for the trees? Or is there a more error free way of doing this.
I think you can greatly simplify your code using the GregorianCalendar inside System.Globalization. Here you can get the week number for a given date like this:
GregorianCalendar gc = new GregorianCalendar();
int weekno = gc.GetWeekOfYear(date, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
You see here that you can give the rules for how to caclulate the week number according to your local rules. Like here in Norway, we have Monday as our first week day, and the first week of the year is the first week that has four or more days. Set this to your culture specific rules to get the correct week numbers.
Some of your specific handling you still ahve to do by hand, but some of the clutter can be removed using this at least :)
why are you not using a DateTimePicker control? it will tell you the day for the user selected date. Then you can simply subtract no. of days from it to get date for monday. For example:
I'm using a DateTimePicker control and named it dtpTemp. the event used is
dtpTemp_ValueChanged()
dtpTemp.Value.DayOfWeek - will give you the day: tuesday, wednesday, thursday etc.
then you can use following code with switch case accordingly:
dtpTemp.Value.AddDays(num); to get date for monday
here num will have -ve values which will depend on day calculated above. Values: -1 for tuesday, -2 for wednesday, -3 for thursday and so on.
plus, using a datetimepicker will also have a positive impact on the UI itself.