Get the default timezone for a country (via CultureInfo)

Question

Is there a program or a table that provides the default timezone for every country?

Yes, the US, Canada, & Russia have multiple timezones. (I think every other c

Answer 1

Some countries have more as one timezone for example russia.

In my solution i use NodaTime if you have a longitude information available i select the best timezone for this country.

var countryName = "Russia";
var longitude = 40.332206;

var zones = TzdbDateTimeZoneSource.Default.ZoneLocations.Where(x => x.CountryName == countryName).AsQueryable();
if (!double.IsNaN(longitude))
{
    zones = zones.OrderBy(o => this.Distance(o.Latitude, longitude, o.Latitude, o.Longitude, DistanceUnit.Kilometer));
}
var bestZone = zones.FirstOrDefault();
var dateTimeZone = TzdbDateTimeZoneSource.Default.ForId(bestZone.ZoneId);

var newTime = DateTime.UtcNow.AddSeconds(dateTimeZone.MaxOffset.Seconds);

Calculate distance of geo coordinates

public enum DistanceUnit { StatuteMile, Kilometer, NauticalMile };

private double Distance(double lat1, double lon1, double lat2, double lon2, DistanceUnit unit)
{
    double rlat1 = Math.PI * lat1 / 180;
    double rlat2 = Math.PI * lat2 / 180;
    double theta = lon1 - lon2;
    double rtheta = Math.PI * theta / 180;
    double dist =
        Math.Sin(rlat1) * Math.Sin(rlat2) + Math.Cos(rlat1) *
        Math.Cos(rlat2) * Math.Cos(rtheta);
    dist = Math.Acos(dist);
    dist = dist * 180 / Math.PI;
    dist = dist * 60 * 1.1515;

    switch (unit)
    {
        case DistanceUnit.Kilometer:
            return dist * 1.609344;
        case DistanceUnit.NauticalMile:
            return dist * 0.8684;
        default:
        case DistanceUnit.StatuteMile: //Miles
            return dist;
    }
}