How do I get the DateTime from the beginning of the week?

How can I just know the current time in C to find the beginning of the week (Sunday and Monday)?

It's like:


#1 building

Ugly, but at least give you the right date

Set the start time of the week through the system:

    public static DateTime FirstDateInWeek(this DateTime dt)
        while (dt.DayOfWeek != System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
            dt = dt.AddDays(-1);
        return dt;


    public static DateTime FirstDateInWeek(this DateTime dt, DayOfWeek weekStartDay)
        while (dt.DayOfWeek != weekStartDay)
            dt = dt.AddDays(-1);
        return dt;

#2 building

Try this code in C, and you can get the start and last dates of a given week. Here Sunday is the first day, Saturday is the last day, but you can set two days according to your culture

DateTime firstDate = GetFirstDateOfWeek(DateTime.Parse("05/09/2012").Date,DayOfWeek.Sunday);
DateTime lastDate = GetLastDateOfWeek(DateTime.Parse("05/09/2012").Date, DayOfWeek.Saturday);

public static DateTime GetFirstDateOfWeek(DateTime dayInWeek, DayOfWeek firstDay)
    DateTime firstDayInWeek = dayInWeek.Date;
    while (firstDayInWeek.DayOfWeek != firstDay)
        firstDayInWeek = firstDayInWeek.AddDays(-1);

    return firstDayInWeek;
public static DateTime GetLastDateOfWeek(DateTime dayInWeek, DayOfWeek firstDay)
    DateTime lastDayInWeek = dayInWeek.Date;
    while (lastDayInWeek.DayOfWeek != firstDay)
        lastDayInWeek = lastDayInWeek.AddDays(1);

    return lastDayInWeek;

#3 building

Put them together through globalization and allow designated days of the week to be part of the conference call

public static DateTime StartOfWeek ( this DateTime dt, DayOfWeek? firstDayOfWeek )
    DayOfWeek fdow;

    if ( firstDayOfWeek.HasValue  )
        fdow = firstDayOfWeek.Value;
        System.Globalization.CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
        fdow = ci.DateTimeFormat.FirstDayOfWeek;

    int diff = dt.DayOfWeek - fdow;

    if ( diff < 0 )
        diff += 7;

    return dt.AddDays( -1 * diff ).Date;


#4 building

Use Fluent DateTime :

var monday = DateTime.Now.Previous(DayOfWeek.Monday);
var sunday = DateTime.Now.Previous(DayOfWeek.Sunday);

#5 building

The fastest way I can think of is:

var sunday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek);

If you want to use other days of the week as the start date, simply add the DayOfWeek value to the end location

var monday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Monday);

var tuesday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Tuesday);

Posted by asurfaceinbetween on Sun, 26 Jan 2020 06:39:53 -0800