public static void Main()
var today=DateOnly.FromDateTime(DateTime.Today);
var start=today.StartOfWeek(DayOfWeek.Monday);
Console.WriteLine(start);
public static class DateTimeExtensions
public static DateOnly StartOfWeek(this DateOnly dt, DayOfWeek startOfWeek)
int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(-1 * diff);
public static DateOnly StartOfMonth(this DateOnly @this)
return new DateOnly(@this.Year, @this.Month, 1);