Miladi and Shamsi to Ghamari

GhamariConvertor.cs

    public static class GhamariDate
    {
        private const decimal GREGORIAN_EPOCH = 1721425.5M;
        private const decimal ISLAMIC_EPOCH = 1948439.5M;

        public static string MiladiToGhamari(DateTime date)
        {
            var result = j_gh(date.Year, date.Month, date.Day);
            return string.Format("{0}/{1}/{2}", result[0], result[1], result[2]);
        }

        public static string ShamsiToGhamari(string date)
        {
            var pc = new System.Globalization.PersianCalendar();
            var result = date.Split('/');
            var dt1 = pc.ToDateTime(Convert.ToInt32(result[0]), Convert.ToInt32(result[1]), Convert.ToInt32(result[2]), 0, 0, 0, 0);
            var zresult = j_gh(dt1.Year, dt1.Month, dt1.Day);
            return string.Format("{0}/{1}/{2}", zresult[0], zresult[1], zresult[2]);
        }

        private static int[] j_gh(int t, int o, int n)
        {
            var julian_update = gregorian_to_jd(t, o, n) + Math.Floor(0.5M) / 86400M;
            return jd_to_islamic(julian_update);
        }

        private static decimal gregorian_to_jd(int t, int o, int n)
        {
            return GREGORIAN_EPOCH - 1 + 365 * (t - 1) + Math.Floor((t - 1) / 4M) +
                -Math.Floor((t - 1) / 100M) + Math.Floor((t - 1) / 400M) + Math.Floor(
                (367M * o - 362M) / 12M + (2 >= o ? 0 : leap_gregorian(t) ? -1 : -
                    2) + n);
        }

        private static bool leap_gregorian(decimal t)
        {
            return t % 4 == 0 && !(t % 100 == 0 && t % 400M != 0);
        }

        private static int[] jd_to_islamic(decimal t)
        {
            t = Math.Floor(t) + 0.5M;
            var o = (int)Math.Floor((30*(t - ISLAMIC_EPOCH) + 10646)/10631);
            var n = (int)Math.Min(12, Math.Ceiling((t - (29M + islamic_to_jd(o, 1, 1)))/29.5M) + 1);
            var e = (int)(t - islamic_to_jd(o, n, 1) + 1);
            return new[] {o, n, e};
        }

        private static decimal islamic_to_jd(decimal t, decimal o, decimal n)
        {
            return n + Math.Ceiling(29.5M * (o - 1)) + 354 * (t - 1) + Math.Floor((3 + 11 * t) / 30) + ISLAMIC_EPOCH - 1;
        }
    }