TimeHelper

using System;

namespace Core {

    /// <summary>
    /// All times are in Universal Time
    /// </summary>
    public static class TimeHelper {

        /// <summary>
        /// Converts the time to Local Time
        /// </summary>
        public static DateTime FromUnixTimeLocal(long seconds) {
            return FromUnixTime(seconds).ToLocalTime();
        }

        /// <summary>
        /// All times are in Universal Time
        /// </summary>
        public static DateTime FromUnixTime(long seconds) {
            var time = new DateTime(1970,1,1,0,0,0,DateTimeKind.Utc);
            time = time.AddSeconds(seconds);
            return time;
        }

        /// <summary>
        /// All times are in Universal Time
        /// </summary>
        public static DateTime? FromUnixTimeNull(string secondsString) {
            if(string.IsNullOrWhiteSpace(secondsString))
                return null;

            long seconds = 0L;

            if(!long.TryParse(secondsString,out seconds))
                return null;

            return FromUnixTime(seconds);
        }
        /// <summary>
        /// All times are in UTC, if the <see cref="dateTime"/> is a local time is is converted to Universal Time
        /// </summary>
        public static long ToUnixTime(DateTime dateTime) {

            if(dateTime.Kind == DateTimeKind.Local)
                dateTime = dateTime.ToUniversalTime();

            var timeSpan = (dateTime - new DateTime(1970,1,1,0,0,0,DateTimeKind.Utc));
            var timestamp = (long)timeSpan.TotalSeconds;

            return timestamp;
        }
    }
}