TelegramBotFramework/TelegramBotBase/Tools/Time.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TelegramBotBase.Tools
{
    public static class Time
    {
        public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
        {
            int diff = dt.DayOfWeek - startOfWeek;
            if (diff < 0)
            {
                diff += 7;
            }
            return dt.AddDays(-1 * diff).Date;
        }

        public static DateTime EndOfWeek(this DateTime dt, DayOfWeek startOfWeek)
        {
            return StartOfWeek(dt, startOfWeek).AddDays(6);
        }

        public static DateTime FirstDayOfMonth(this DateTime date)
        {
            return new DateTime(date.Year, date.Month, 1);
        }

        public static DateTime LastDayOfMonth(this DateTime date)
        {
            return FirstDayOfMonth(date).AddMonths(1).AddDays(-1);
        }
    }
}