find week ending date of last completed week

Question

For any given date, how would you find the week ending date of the last completed week, if your week runs from Sunday to Saturday?

Answer 1

DateTime givenDate; // = ...
int daysToOffset = ((int)givenDate.DayOfWeek + 1) * -1;
DateTime lastDayOfLastCompletedWeek = givenDate.AddDays(daysToOffset);

Answer 2

DateTime StartOfWeek = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek);
DateTime EndOfLastWeek = StartOfWeek.AddDays(-1);

Answer 3

    public static DateTime EndOfWeek(DateTime dateTime)
    {
        DateTime start = StartOfWeek(dateTime);

        return start.AddDays(6);
    }

    public static DateTime StartOfWeek(DateTime dateTime)
    {
        int days = dateTime.DayOfWeek - DayOfWeek.Monday; 

        if (days < 0) 
            days += 7;

        return dateTime.AddDays(-1 * days).Date;
    }

To find the end of the previous week, just call:

    DateTime endPrevWeek = StartOfWeek(DateTime.Today).AddDays(-1);

Answer 4

If you want to specify which day is the end of week, and you don't want to worry about what day the system has defined as the default start of the week, use this method:

private static DateTime GetPreviousSpecifiedDayOfWeek(DateTime dt, DayOfWeek day)
    {
        if (dt.DayOfWeek == day)
        {
            return dt;
        }

        while (dt.DayOfWeek != day)
        {
            dt = dt.AddDays(-1);
        }

        return dt;
    }

Answer 5

.NET DateTimes expose a DayOfWeek property. You can leverage that in this case:

var currDay = DateTime.Today.DayOfWeek;
//currday is now an enumeration with Sunday=0, Saturday=6
//We can cast that to a number and subtract to get to the previous Saturday
var EndOfLastWeek = DateTime.Today.AddDays(((int)currDay+1)*-1);