/// <summary>
/// Calculate and return timezone.
/// </summary>
/// <param name="tz">Input string.</param>
/// <returns>Parsed timezone.</returns>
public static string TimeZoneToOffset(string tz)
{
if (tz == null)
{
return(null);
}
tz = tz.ToUpper().Trim();
if (TimeZones.ContainsKey(tz))
{
return(TimeZones[tz].First());
}
return(null);
}