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using System;
using System.Globalization;

namespace XenCenterLib
{
    public class TimeUtil
    {
        public const long TicksBefore1970 = 621355968000000000;

        public const string ISO8601DateFormat = "yyyyMMddTHH:mm:ssZ";

        public static long TicksToSeconds(long ticks)
        {
            return ticks / 10000000;
        }

        public static long TicksToSecondsSince1970(long ticks)
        {
            return (long)Math.Floor(new TimeSpan(ticks - (TicksBefore1970)).TotalSeconds);
        }

        /// <summary>
        /// Parses an ISO 8601 date/time into a DateTime.
        /// </summary>
        /// <param name="toParse">Must be of the format yyyyMMddTHH:mm:ssZ. Must not be null.</param>
        /// <returns>The parsed DateTime with Kind DateTimeKind.Utc.</returns>
        public static DateTime ParseISO8601DateTime(string toParse)
        {
            return DateTime.ParseExact(toParse, ISO8601DateFormat, CultureInfo.InvariantCulture, DateTimeStyles.AdjustToUniversal);
        }

        public static string ToISO8601DateTime(DateTime t)
        {
            return t.ToUniversalTime().ToString(ISO8601DateFormat, CultureInfo.InvariantCulture);
        }
    }
}
