How do I convert from unix epoch time and account for daylight saving time in C#?

Question

I have a function that converts from unix epoch time to a .NET DateTime value:

public static DateTime FromUnixEpochTime(double unixTime )
{
  DateTime d = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
  return d.AddSeconds(unixTime);
}

Where I am (UK) the clocks go one hour forward for summer time.

In Python I get the local Epoch time using time.time() (and for the sake of argument, right now the time is 17:15:00) which gives me a value of 1286122500.

If I convert this back to a human readable time using time.localtime() it converts back to 17:15 as I would expect.

How do I convert unix epoch time back to a .NET DateTime value AND account for local daylight savings time. My function above converts 1286122500 back to 16:15 which is incorrect for my geographic location.

Answer 1

Use DateTime.ToLocalTime():

http://msdn.microsoft.com/en-us/library/system.datetime.tolocaltime.aspx

public static DateTime FromUnixEpochTime(double unixTime)
{
    DateTime d = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
    d = d.AddSeconds(unixTime);
    return d.ToLocalTime();
}

Answer 2

The TimeZoneInfo class is great at helping one deal with different times and time zones. It uses the time zone information that Windows has built in to convert between different time zones.

Here's how you'd use it for your problem:

//Get your unix epoch time into a DateTime object
DateTime unixTime = 
    new DateTime(1970,1,1,0,0,0, DateTimeKind.Utc).AddSeconds(1286122500);

//Convert to local time
DateTime localTime = TimeZoneInfo.ConvertTime(unixTime, TimeZoneInfo.Local);

TimeZoneInfo.Local returns the TimeZoneInfo that represents the local time zone.