Develop Reference

DateTime Resets at midnight

Hi I am using C# web app on visual studio.
I have written code to be able to distinguish if the time is between 6am-2pm - 2pm-10pm and 10pm - 6am...
The code runs like a dream for the 6-2 - 2-10 times but for the 10pm - 6am.. the code runs fine until midnight and then it just resets my counter to 0 and stays at 0 until 6am.. I can't get my head around why this is doing.. Does anybody have a solution..
public DateTime Shiftstart { get; set; }
public DateTime Shiftend { get; set; }
public string Itemseriesmaster { get; set; }
public string SeriesMasterId { get; set; }
public void CalcShiftPeriod() //constructor
{
DateTime now = DateTime.Now; //date time now
int currentHour = now.Hour; //hour now
int shiftHourStart;
if (currentHour >= 6 && currentHour <= 13)
{
shiftHourStart = 6;
}
else if (currentHour >= 14 && currentHour <= 21)
{
shiftHourStart = 14;
}
else
{
shiftHourStart = 22;
}
Shiftstart = now.Date.AddHours(shiftHourStart);
Shiftend = Shiftstart.AddHours(7);
Shiftend = Shiftend.AddMinutes(59);
Shiftend = Shiftend.AddSeconds(59);
}
The code is calculating total units packed and is working fine, and resets after the given time on both the 6-2 and 2 - 10 shifts..
Until it gets to the 10pm - 6am and then just completely stops at midnight.
BizManager biz = new BizManager();
DataTable dt = new DataTable();
if (DDLProduct.SelectedValue.Equals("G120C-2") || DDLProduct.SelectedValue.Equals("G120 PM240-2") )
{
RefreshMainGridTht(selectedProduct, shiftStart, shiftEnd
);
}
dt = biz.GetPacktstatisticsForShift(shiftStart, shiftEnd, selectedProduct);
GridView1.DataSource = dt.DefaultView;
GridView1.DataBind();
int sumActual = 0;
int sumTarget = 0;
biz.CalculatePackingTotals(dt, out sumActual, out sumTarget);
LabelTotal.Text = sumActual.ToString();
DateTime dtmNow = DateTime.Now;
TimeSpan tsIntoShift = dtmNow - shiftStart;
TimeSpan tsTotalShift = shiftEnd - shiftStart;
double p = tsIntoShift.TotalMinutes / tsTotalShift.TotalMinutes;
int adjustedTarget = Convert.ToInt32(sumTarget * p);
if (sumActual > sumTarget)
{
LabelTotal.ForeColor = Color.Lime;
}
else
{
LabelTotal.ForeColor = Color.Red;
}
}
catch (Exception ex)
{
ErrMsg = App.HandleError(MethodBase.GetCurrentMethod(), ex, string.Empty);

You have to distinguish between currentHour from 0 to 5 and currentHour from 22 to 23.
For example, consider currentHour is 1. Your calculation says that the shift starts at 22:00 of the current day (now.Date.AddHours(22)), which is obviously wrong because the shift already started at 22:00 of the previous day.
So from currentHour 0 to 5 you have to subtract a day from your Shiftstart.
One possible way to do that would be to set shiftHourStart to -2 for currentHour between 0 and 5.
if (currentHour < 6)
{
shiftHourStart = -2;
}
else if (currentHour >= 6 && currentHour <= 13)
{
shiftHourStart = 6;
}
else if (currentHour >= 14 && currentHour <= 21)
{
shiftHourStart = 14;
}
else
{
shiftHourStart = 22;
}

The error lies in adding the hours to the current day...
Shiftstart = now.Date.AddHours(shiftHourStart);
At 23:59 you are adding 22 hours to "2018-11-06".
One minute passes...
At 00:00 you are adding 22 hours to "2018-11-07".
That means your start time moves 24 hours over the course of that one minute.
You could distinguish this scenario as part of your if-statement. See the comments a) and b) below.
int currentHour = now.Hour;
DateTime date = now.Date; // a) This is today in most cases...
int shiftHourStart;
if (currentHour >= 6 && currentHour <= 13)
{
shiftHourStart = 6;
}
else if (currentHour >= 14 && currentHour <= 21)
{
shiftHourStart = 14;
}
else if (currentHour >= 22)
{
shiftHourStart = 22;
}
else
{
// midnight to 6am
date = date.AddDays(-1); // b) But not in this case
shiftHourStart = 22;
}

First store your time in a TimeSpan this will give you more flexibility if tomorrow shift start and ends at 30min. Then store those Timespan in a class that represent the time frame. And if you have a list of them make it a List. It will help reading and maintaining your code. For now it's a brunch of magic numbers.
To check if a time is in a Range, I used :
public static bool IsBetween(TimeSpan time, TimeSpan start, TimeSpan end)
=> (start <= end) ? time >= start && time <= end : time >= start || time <= end;
internal void TestMethod()
{
var timeSlots = new[] {
new TimeFrame { start= new TimeSpan(6,0,0) , end = new TimeSpan(13,0,0) },
new TimeFrame { start= new TimeSpan(14,0,0) , end = new TimeSpan(21,0,0) },
new TimeFrame { start= new TimeSpan(22,0,0) , end = new TimeSpan(6,0,0) }
};
var today = DateTime.Today;
var dayHours = Enumerable.Range(0, 24).Select(x => today.AddHours(x)).ToList();
foreach (var currentDateTime in dayHours)
{
var matchingRanges = timeSlots.Where(x => IsBetween(currentDateTime .TimeOfDay, x.start, x.end));
if (matchingRanges.Any())
{
var temp = matchingRanges.First();
Console.WriteLine($"-> {currentDateTime } is in range {temp.start}-{temp.end}");
Console.WriteLine($"\t ShiftHours= {temp.start}-{temp.end.Subtract(new TimeSpan(0, 0, 1))}");
}
else
{
Console.WriteLine($"no Match for {currentDateTime }");
}
}
}
As you added a comment about testing it at midnight , included a TestMethod where I create all hours of a day (from 00h to 23h) so you can easly see what going on.

Check if a datetime is in same week as other datetime

Let's say I have a list of dates in a table. Now I want to find all rows, which is in the same week as the date provided as an argument.
Let's say I have a table with:
2014-09-11
2014-09-12
2014-09-15
And I give this function the argument 2014-09-09, it has to look from monday->sunday, and realize that 09-11 and 09-12 is part of the week, but not 09-15.
How on earth to solve this?
I have thought on making a check on year, month and weeknumber, but you cannot guarantee that month is the same...
So how do you solve a problem like this?

DxCk's comment is valid. This solution will work even if the first or last week of the year cross two different years:
Check that the first day of the week for both dates fall on the same day.
Here is the code:
private bool DatesAreInTheSameWeek(DateTime date1, DateTime date2)
{
var cal = System.Globalization.DateTimeFormatInfo.CurrentInfo.Calendar;
var d1 = date1.Date.AddDays(-1 * (int)cal.GetDayOfWeek(date1));
var d2 = date2.Date.AddDays(-1 * (int)cal.GetDayOfWeek(date2));
return d1 == d2;
}

why not?
bool AreFallingInSameWeek(DateTime date1, DateTime date2)
{
return date1.AddDays(-(int)date1.DayOfWeek) == date2.AddDays(-(int)date2.DayOfWeek);
}
if you want to use any day other than Sunday as start of the week
bool AreFallingInSameWeek(DateTime date1, DateTime date2, DayOfWeek weekStartsOn)
{
return date1.AddDays(-GetOffsetedDayofWeek(date1.DayOfWeek, (int)weekStartsOn)) == date2.AddDays(-GetOffsetedDayofWeek(date2.DayOfWeek, (int)weekStartsOn));
}
int GetOffsetedDayofWeek(DayOfWeek dayOfWeek, int offsetBy)
{
return (((int)dayOfWeek - offsetBy + 7) % 7)
}

Check the DateTime.Year and Calendar.GetWeekOfYear(DateTime, ...). No need to check for the month.
EDIT: This is wrong but I can't delete it. See #Sparrow's answer below.

Use: public virtual int GetWeekOfYear(DateTime time,CalendarWeekRule rule,DayOfWeek firstDayOfWeek) of Calendar class

My requirement was to find DOBs falling on the current week. Hope this helps with your doubt. Basically the idea behind this code is as follows:
Change the DOB to current year birthday (eg; 24-02-1988 to 24-02-2018(current year).
Add a year, if the brithday week contains both dec and jan
Get the first day of today's week.
Get last day of today's week.
check if the current year birthday falls between first day and last day of today's week.
private bool DatesAreInTheSameWeek(DateTime birthday)
{
if (birthday == DateTime.MinValue)
{
return false;
}
else
{
var birtdayWithCurrentYear = new DateTime(DateTime.Today.Year, birthday.Month, birthday.Day);
if (birthday.Month == 1 && DateTime.Today.Month != 1)
{
birtdayWithCurrentYear = birtdayWithCurrentYear.AddYears(1);
}
DateTime firstDayInWeek = DateTime.Today.Date;
while (firstDayInWeek.DayOfWeek != CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
firstDayInWeek = firstDayInWeek.AddDays(-1);var lastDayInWeek = firstDayInWeek.AddDays(7);
return birtdayWithCurrentYear < lastDayInWeek && birtdayWithCurrentYear >= firstDayInWeek;
}
}

Since the accepted answer contains error as #DxCK mentioned in comment, here is my solution for this:
public static class DateExtensions
{
private static void Swap<T>(ref T one, ref T two)
{
var temp = one;
one = two;
two = temp;
}
public static bool IsFromSameWeek(this DateTime first, DateTime second, DayOfWeek firstDayOfWeek = DayOfWeek.Monday)
{
// sort dates
if (first > second)
{
Swap(ref first, ref second);
}
var daysDiff = (second - first).TotalDays;
if (daysDiff >= 7)
{
return false;
}
const int TotalDaysInWeek = 7;
var adjustedDayOfWeekFirst = (int)first.DayOfWeek + (first.DayOfWeek < firstDayOfWeek ? TotalDaysInWeek : 0);
var adjustedDayOfWeekSecond = (int)second.DayOfWeek + (second.DayOfWeek < firstDayOfWeek ? TotalDaysInWeek : 0);
return adjustedDayOfWeekSecond >= adjustedDayOfWeekFirst;
}
}
Also here is link to another correct solution with slightly different approach.

Find start and end dates for the first date's week. Then check if the second date is between those two.
public static bool DateInsideOneWeek(DateTime date1, DateTime date2)
{
DayOfWeek firstDayOfWeek = System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek;
DateTime startDateOfWeek = date1.Date;
while(startDateOfWeek.DayOfWeek != firstWeekDay)
{ startDateOfWeek = startDateOfWeek.AddDays(-1d); }
DateTime endDateOfWeek = startDateOfWeek.AddDays(6d);
return date2 >= startDateOfWeek && date2 <= endDateOfWeek;
}

If you don't want to use the Calendar class you can use this function:
public static int WeekOfYear(DateTime dt)
{
int startDays = 0;
// first day of the year
DateTime firstJanuary = new DateTime(dt.Year, 1, 1);
if (firstJanuary.DayOfWeek == DayOfWeek.Tuesday)
{
startDays = 1;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Wednesday)
{
startDays = 2;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Thursday)
{
startDays = 3;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Friday)
{
startDays = 4;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Saturday)
{
startDays = 5;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Sunday)
{
startDays = 6;
}
if (DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek == DayOfWeek.Sunday)
{
startDays++;
startDays = startDays % 7;
}
return ((dt.DayOfYear + startDays - 1) / 7) + 1;
}

Accepted answer doesn't work for a french calendar and when the dates are 03/10/2022 and 09/10/2022.
This worked for me :
public static partial class DateTimeExtensions
{
public static DateTime FirstDayOfWeek(this DateTime dt)
{
var culture = System.Threading.Thread.CurrentThread.CurrentCulture;
var diff = dt.DayOfWeek - culture.DateTimeFormat.FirstDayOfWeek;
if (diff < 0)
{
diff += 7;
}
return dt.AddDays(-diff).Date;
}
public static DateTime LastDayOfWeek(this DateTime dt) =>
dt.FirstDayOfWeek().AddDays(6);
public static DateTime FirstDayOfMonth(this DateTime dt) =>
new DateTime(dt.Year, dt.Month, 1);
public static DateTime LastDayOfMonth(this DateTime dt) =>
dt.FirstDayOfMonth().AddMonths(1).AddDays(-1);
public static DateTime FirstDayOfNextMonth(this DateTime dt) =>
dt.FirstDayOfMonth().AddMonths(1);
public static int GetWeeekNumber(this DateTime dt)
{
CultureInfo culture = System.Threading.Thread.CurrentThread.CurrentCulture;
Calendar myCal = culture.Calendar;
// Gets the DTFI properties required by GetWeekOfYear.
CalendarWeekRule myCWR = culture.DateTimeFormat.CalendarWeekRule;
DayOfWeek myFirstDOW = culture.DateTimeFormat.FirstDayOfWeek;
return myCal.GetWeekOfYear(dt, myCWR, myFirstDOW);
}
public static bool IsInTheSameWeek(this DateTime date1, DateTime date2)
{
return date1.GetWeeekNumber() == date2.GetWeeekNumber();
}
}
Usage :
item.Week.IsInTheSameWeek(Week)

How can I ckeck that the current time is within a specific time range?

I need to compare that the current time is within a specific range. I've tried the following
DateTime currentTime = DateTime.Now;
int Comaprestart = DateTime.Compare(currentTime, startTime);
int CompareEnd = DateTime.Compare(currentTime,endTime);
if ((Comaprestart >= 0) && (CompareEnd <= 0))
LinkBtnQuiz.Enabled = true;
It doesn't work right. for example I have the end time equal '2014-06-08 13:30:00.000' and the current time equal '2014-06-08 13:12:00.000' but I get CompareEnd=1 while it should be -1 as the current time is earlier than the end time.
Any idea of what is causing the error??

you can do it easier:
if(currentTime >= startTime && currentTime <= endTime)
{
LinkBtnQuiz.Enabled = true;
}

return dateToCheck >= startDate && dateToCheck < endDate;
Check this answer How to know if a DateTime is between a DateRange in C#

How to get the 4. Wednesday of the next Month as DateTime?

I need a function which gives me the nth DateTime of the next Month.
For Example: I need the 4th Wednesday of next Month.
My code delivers a wrong Date:
private static DateTime FindNextDay(DayOfWeek dayOfWeek, DateTime fday, Int32 instance)
{
DateTime day = new DateTime(fday.Year, fday.Month, 1, fday.Hour, fday.Minute, fday.Second);
// DateTime day is in this Example= 2014-08.01 11.00 AM
if (instance == 2)
{
day = day.AddDays(7);
}
else if (instance == 3)
{
day = day.AddDays(14);
}
else if (instance == 4) //if the 4th week is requested
{
day = day.AddDays(28); // i add 28 days
}
while (day.DayOfWeek != dayOfWeek)
{
day = day.AddDays(1); // and search the wednesday and return it back
}
return day;
}
Could you show me a better solution?

Something like this..
Get the first day of the next month, keep a count of the number of wednesdays you've encountered adding to it when you find one. Return when the count is 4.
private static DateTime GetFourthWednesday()
{
DateTime firstOfMonth = new DateTime(DateTime.Now.AddMonths(1).Year, DateTime.Now.AddMonths(1).Month, 1);
int count = 0;
while (count < 4)
{
if (firstOfMonth.DayOfWeek == DayOfWeek.Wednesday)
{
count++;
}
if (count == 4)
{
return firstOfMonth;
}
firstOfMonth = firstOfMonth.AddDays(1);
}
return firstOfMonth;
}
Gives 27/08/2014 if run today

Change the last else if to:
else if (instance == 4) //if the 4th week is requested
{
day = day.AddDays(21); // i add 28 days
}
You should add 21 days not 28.

Since because I'm too lazy, I wrote my code like;
DateTime firstDayOfNextMonth = new DateTime(2014, DateTime.Now.Month + 1, 1);
int count = 0;
if (firstDayOfNextMonth.DayOfWeek == DayOfWeek.Wednesday)
count = 1;
while (count != 4)
{
firstDayOfNextMonth = firstDayOfNextMonth.AddDays(1);
if (firstDayOfNextMonth.DayOfWeek == DayOfWeek.Wednesday)
count++;
}
Console.WriteLine(firstDayOfNextMonth);
Basicly, I check if the first day of next month is Wednesday or not, then I iterate my DateTime to found 4. Wednesday in next month.
It is working for today and it prints 27.08.2014 which is fourth Wednesday of next month.
You can write an extension method like;
public static class DateTimeExtensions
{
public static void FindInstanceNextMonth(DateTime Now, DayOfWeek day, int instance)
{
DateTime firstDayOfNextMonth = new DateTime(Now.Year, Now.Month + 1, 1);
int count = 0;
if (firstDayOfNextMonth.DayOfWeek == day)
count = 1;
while (count != instance)
{
firstDayOfNextMonth = firstDayOfNextMonth.AddDays(1);
if (firstDayOfNextMonth.DayOfWeek == day)
count++;
}
Console.WriteLine(firstDayOfNextMonth);
}
}
And call it as;
DateTimeExtensions.FindInstanceNextMonth(DateTime.Now,
DayOfWeek.Wednesday,
4);

Compare system Day and DateTime

I'm using the code below to compare two Times:
DateTime systemtime = DateTime.Now;
DateTime timestart = Convert.ToDateTime(txtTimestart.Text);
DateTime timeend = Convert.ToDateTime(txtTimeend.Text);
if (systemtime < timestart || systemtime > timeend)
{
MessageBox.Show("not auth.");
}
else
{
MessageBox.Show("auth.");
}
But I also want to compare the current day. For example, if today is Monday or Thursday, the user is authenticated, not if otherwise. How do I do it? Thanks.

DateTime systemtime = DateTime.Now;
if(systemtime.DayOfWeek == DayOfWeek.Monday)
{
...
}

timestart.DayOfWeek will give you values like DayOfWeek.Thursday or DayOfWeek.Friday etc.
See here for documentation and an example: http://msdn.microsoft.com/en-us/library/system.datetime.dayofweek.aspx

The DateTime object will have a property DayOfWeek.
You could just compare the string.

try this
var systemtime = DateTime.Now;
var start = "Monday";
var finish = "Wednesday";
DayOfWeek startDay;
if (!Enum.TryParse<DayOfWeek>(start ,out startDay))
{
//handle parse error
}
DayOfWeek finishDay;
if (!Enum.TryParse<DayOfWeek>(finish, out finishDay))
{
//handle parse error
}
if (systemtime.DayOfWeek < startDay || systemtime.DayOfWeek > finishDay)
{
MessageBox.Show("not auth.");
}
else
{
MessageBox.Show("auth.");
}