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c#datetimetimeutc

Why local datetime has the same timestamp with utc datetime, no matter its DateTime or DateTImeOffset?

I have checked this question DateTime local and utc the same, but still have no idea.

Here's my code

DateTime localNow = DateTime.Now;
DateTime utcNow = DateTime.UtcNow;
Int64 localTimeStamp = ((DateTimeOffset)localNow).ToUnixTimeSeconds();
Int64 utcTimeStamp = ((DateTimeOffset)utcNow).ToUnixTimeSeconds();

Console.WriteLine("With Datetime");
Console.WriteLine("Current time: " + localNow.ToString("yyyy/MM/dd HH:mm:ss") + " timestamp: " + localTimeStamp);
Console.WriteLine("Current Utc time: " + utcNow.ToString("yyyy/MM/dd HH:mm:ss") + " timestamp: " + utcTimeStamp);

DateTimeOffset localNowOff = DateTimeOffset.Now;
DateTimeOffset utcNowOff = DateTimeOffset.UtcNow;
Int64 localOffTimeStamp = localNowOff.ToUnixTimeSeconds();
Int64 utcOffTimeStamp = utcNowOff.ToUnixTimeSeconds();
Console.WriteLine("With DatetimeOffset");
Console.WriteLine("Current time: " + localNowOff.ToString("yyyy/MM/dd HH:mm:ss") + " timestamp: " + localOffTimeStamp);
Console.WriteLine("Current Utc time: " + utcNowOff.ToString("yyyy/MM/dd HH:mm:ss") + " timestamp: " + utcOffTimeStamp);

And heres' the output:

With Datetime
Current time: 2023/10/31 23:11:33 timestamp: 1698765093
Current Utc time: 2023/10/31 15:11:33 timestamp: 1698765093

With DatetimeOffset
Current time: 2023/10/31 23:11:33 timestamp: 1698765093
Current Utc time: 2023/10/31 15:11:33 timestamp: 1698765093

I don't believe the timestamp result between local ant utc should be the same, but it did happen.

However, when i try get local datetime from the timestamp, it turns out to be utc datetime, like this:

DateTime localNow = DateTime.Now;
Int64 localTimeStamp = ((DateTimeOffset)localNow).ToUnixTimeSeconds();
DateTime localDateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Local);
localDateTime = localDateTime.AddSeconds(localTimeStamp).ToLocalTime();
Console.WriteLine("Convert local timestamp to datetime: " + localDateTime.ToString("yyyy/MM/dd HH:mm:ss"));

So am i doing anything wrong and what's the proper way to get the timestamp about local time and utc time and convert back to datetime?

Solution

  • There is no local unix timestamp as the epoch unix timestamp is always UTC+0.

    If you want to convert the timestamp to local do something like this:

    DateTimeOffset dt = DateTimeOffset.FromUnixTimeSeconds(1698766249);
DateTime localDt = dt.LocalDateTime;