时间日历判断闰年或者平年

/// <summary>
/// 根据所选时间(年和月)得到当月日历表
/// </summary>
public class CalenderDT
{
    public DataTable Convert(int year, int month)
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("星期日", typeof(String));
        dt.Columns.Add("星期一", typeof(String));
        dt.Columns.Add("星期二", typeof(String));
        dt.Columns.Add("星期三", typeof(String));
        dt.Columns.Add("星期四", typeof(String));
        dt.Columns.Add("星期五", typeof(String));
        dt.Columns.Add("星期六", typeof(String));
        DataRow dr;
        int days = GetDaysOfMonth(year, month);
        int firstDayOfMonth = GetWeekOfDate(year, month, 1);
        dr = dt.NewRow();
        for (int i = 1; i <= days; i++)
        {
            dr[(firstDayOfMonth+i-1) % 7] = i;
            if (GetWeekOfDate(year, month, i) == 6)
            {
                dt.Rows.Add(dr);
                dr = dt.NewRow();
            }
        }
        dt.Rows.Add(dr);
        return dt;
    }
 
    #region 判断是否为闰年
    public static bool IsleapYear(int year)
    {
        if ((year % 4 == 0 && year % 100 != 100) || year % 400 == 0)
        {
            return true;
        }
        else
            return false;
    }
    #endregion
 
    #region 判断一个月有多少天
    public static int GetDaysOfMonth(int year, int month)
    {
        int days = 0;
 
        switch (month)
        {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                days = 31;
                break;
            case 4:
            case 6:
            case 9:
            case 11:
                days = 30;
                break;
            case 2:
                days = IsleapYear(year) ? 29 :28;
                break;
            default:
                days = 30;
                break;
        }
        return days;
    }
    #endregion
 
    #region 判断一年有多少天
    public static int GetDaysOfYear(int year)
    {
        return IsleapYear(year) ? 366 : 365;
    }
    #endregion
 
    #region 时间的星期
    public static int GetWeekOfDate(int year, int month, int day)
    {
        int days = GetDaysOfDate(year, month, day);
        return (days + 2) % 7;
    }
    #endregion
 
    #region 判断该日是星期几
    public static string GetWeek(string str)
    {
        string[] strs = str.Split('-');
        int week=GetWeekOfDate(int.Parse(strs[0]), int.Parse(strs[1]), int.Parse(strs[2]));
        switch (week)
        {
            case 1:
                return "星期一";
            case 2:
                return "星期二";
            case 3:
                return "星期三";
            case 4:
                return "星期四";
            case 5:
                return "星期五";
            case 6:
                return "星期六";
            case 7:
                return "星期日";
            default:
                return "星期日";
        }
    }
    #endregion
 
    #region 距离1980年有多少天
    public static int GetDaysOfDate(int year, int month, int day)
    {
        int totalDays = 0;
        for (int i = 1980; i < year; i++)
        {
            totalDays = totalDays + GetDaysOfYear(i);
        }
        for (int i = 1; i < month; i++)
        {
            totalDays += GetDaysOfMonth(year, i);
        }
        totalDays = totalDays + day - 1;
        return totalDays ;
    }
    #endregion
}