Time Zone Helper Class

TimeZoneHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Snippet.Helpers.Timezone
{
    /// <summary>
    /// Class TimeZoneHelper.
    /// </summary>
    public static class TimeZoneHelper
    {
        /// <summary>
        /// Outputs a list of all the supported time zones
        /// </summary>
        /// <returns>IEnumerable&lt;TimeZoneItem&gt;.</returns>
        public static IEnumerable<TimeZoneItem> List()
        {
            var tz = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");

            if (tz.IsDaylightSavingTime(DateTime.Now))
            {
                var timeData = new List<TimeZoneItem>();
                timeData.Add(new TimeZoneItem { Name = "(UTC-07:00) Pacific Time", Id = "Pacific Standard Time" });
                timeData.Add(new TimeZoneItem { Name = "(UTC-07:00) Arizona", Id = "US Mountain Standard Time" });
                timeData.Add(new TimeZoneItem { Name = "(UTC-06:00) Mountain Time", Id = "Mountain Standard Time" });
                timeData.Add(new TimeZoneItem { Name = "(UTC-05:00) Central Time", Id = "Central Standard Time" });

                return timeData;
            }
            else
            {
                var timeData = new List<TimeZoneItem>();
                timeData.Add(new TimeZoneItem { Name = "(UTC-08:00) Pacific Time", Id = "Pacific Standard Time" });
                timeData.Add(new TimeZoneItem { Name = "(UTC-07:00) Arizona", Id = "US Mountain Standard Time" });
                timeData.Add(new TimeZoneItem { Name = "(UTC-07:00) Mountain Time", Id = "Mountain Standard Time" });
                timeData.Add(new TimeZoneItem { Name = "(UTC-06:00) Central Time", Id = "Central Standard Time" });

                return timeData;
            }
        }

        /// <summary>
        /// Converts a time from the specified time zone to UTC
        /// </summary>
        /// <param name="time">The time.</param>
        /// <param name="timeZone">The time zone.</param>
        /// <returns>DateTime.</returns>
        public static DateTime ToUtc(this DateTime time, string timeZone)
        {
            var tz = TimeZoneInfo.FindSystemTimeZoneById(timeZone);

            return TimeZoneInfo.ConvertTimeToUtc(time, tz);
        }

        /// <summary>
        /// Converts a time from UTC to the specified time zone
        /// </summary>
        /// <param name="time">The time.</param>
        /// <param name="timeZone">The time zone.</param>
        /// <returns>DateTime.</returns>
        public static DateTime FromUtc(this DateTime time, string timeZone)
        {
            var tz = TimeZoneInfo.FindSystemTimeZoneById(timeZone);

            return TimeZoneInfo.ConvertTimeFromUtc(time, tz);
        }

        /// <summary>
        /// Converts a timezone to the display name for the passed time (daylight time or standard time)
        /// </summary>
        /// <param name="timeZone">The time zone.</param>
        /// <param name="date">The date.</param>
        /// <returns>System.String.</returns>
        public static string ToName(this string timeZone, DateTime date)
        {
            var tz = TimeZoneInfo.FindSystemTimeZoneById(timeZone);
            return tz.IsDaylightSavingTime(date) ? tz.DaylightName : tz.Id;
        }

        /// <summary>
        /// Converts a long timezone to it's abbreviation
        /// </summary>
        /// <param name="timeZone">The time zone.</param>
        /// <param name="date">The date.</param>
        /// <returns>System.String.</returns>
        public static string ToShortTimeZone(this string timeZone, DateTime date)
        {
            var tzInfo = TimeZoneInfo.FindSystemTimeZoneById(timeZone);

            var tz = tzInfo.IsDaylightSavingTime(date) ? tzInfo.DaylightName.Split(' ') : timeZone.Split(' ');
            return tz.Aggregate(string.Empty, (current, t) => current + t.Substring(0, 1));
        }
    }
    
    /// <summary>
    /// Class TimeZoneItem.
    /// </summary>
    public class TimeZoneItem
    {
        /// <summary>
        /// Gets or sets the identifier.
        /// </summary>
        /// <value>The identifier.</value>
        public string Id { get; set; }

        /// <summary>
        /// Gets or sets the value.
        /// </summary>
        /// <value>The value.</value>
        public string Name { get; set; }
    }    
}