Converting NodaTime to Unix timestamp and the importance of LocalDateTime

问题

I am currently using NodaTime based on my frustrations dealing with timezones in C#'s DateTime class. So far, I'm really pleased.

public static string nodaTimeTest(string input)
{
    var defaultValue = new OffsetDateTime(new LocalDateTime(2000, 1, 1, 0, 0), Offset.Zero);
    var pattern = OffsetDateTimePattern.Create("yyyy-MM-dd'T'HH:mm:sso<m>", CultureInfo.InvariantCulture, defaultValue);
    var result = pattern.Parse(input).Value;

    return result.ToString();
}

I have three specific questions. Above is the method I use where I parse in dateTime strings. I have a format string which allows me how to parse the input. My questions are:

Does it matter what my LocalDateTime(..) is? The method I used is Matt Johnson's Stack example, and his came with the date 2000, 1, 1, 0, 0. I thought that was odd, since most date classes I know use the Epoch time 1970, 1, 1, 0 ,0, so I changed my method to contain the Epoch date, but the outputs were the same:

How do I convert the time to a Unix timestamp? It does not appear there's a built-in method to do so.

Using this method:

    public static string nodaTimeTest6(string input, int timeZone)
    {
        // var defaultValue = new OffsetDateTime(new LocalDateTime(2000, 1, 1, 0, 0), Offset.Zero);
        var defaultValue = new OffsetDateTime(new LocalDateTime(2000, 1, 1, 0, 0), Offset.FromHours(timeZone));
        var pattern = OffsetDateTimePattern.Create("yyyy-MM-dd'T'HH:mm:sso<m>", CultureInfo.InvariantCulture, defaultValue);
        var result = pattern.Parse(input);

        return result.Value.ToString();
    }

I'm testing out the abilities of NodaTime with this method -- specifically, I was wondering if I can parse in a date/time that HAS offset defined inside, and at the same time, my timeZone input also allows input of timezones/offsets. Interestingly enough, my input timeZone gets ignored, so the offset in my output of nodaTimeTest6 is the input date string:

Is this desired behavior?

回答1:

Does it matter what my LocalDateTime(..) is?

The OffsetDateTimePattern.Create method requires a default value. It's only used if the parsing were to fail and you didn't check result.Success before using result.Value.
The other patterns have an overload that doesn't require a default value (see issue #267). I chose the particular default value of 2000-01-01T00:00:00.0000000+00:00 because it's similar to what the other patterns use when you don't specify a default explicitly.
There really isn't any significance though. You can use any default you wish.

How do I convert the time to a Unix timestamp? It does not appear there's a built-in method to do so.

The result.Value is an OffsetDateTime. The Instant type uses the Unix epoch, so you can do this:
```
int unixTime = result.Value.ToInstant().Ticks / NodaConstants.TicksPerSecond;
```
Note that Unix timestamps are precise to the nearest second. If you're passing to JavaScript, you'd want to use TicksPerMillisecond and return it in a long.

... I was wondering if I can parse in a date/time that HAS offset defined inside, and at the same time, my timeZone input also allows input of timezones/offsets.

Sorry, but I don't fully understand what you're asking here. Can you please clarify?
From the code you provided, it looks like you are confusing the offset for the default value with the offset for the input string. The default value is only used if parsing fails.
If you want to control the offset instead of including it in the input, then use a LocalDateTimePattern instead of an OffsetDateTimePattern to do the parsing. After it's parsed, you can associated it with a particular zone.
Also, watch your naming conventions. int timeZone doesn't make sense (that's an offset, not a time zone). Perhaps int offsetHours, or better yet, Offset timeZoneOffset.

来源：https://stackoverflow.com/questions/22389644/converting-nodatime-to-unix-timestamp-and-the-importance-of-localdatetime

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nodatime