Validate System.DateTime is in a UTC format

Question

I have a requirement to store all of the dates recorded in database must be recorded as UTC. So far I can achieve this using Noda library with following method:

    public static DateTime NowUtc(string timeZoneId)
    {
        var timeZone = GetTimeZone(timeZoneId);
        var instant = SystemClock.Instance.Now;
        return instant.InZone(timeZone).ToDateTimeUtc();
    }

I'm going to validate every date that passed into data access layer must be in UTC format.

How do I achieve that?

Thanks

Note: I have created a custom class library that used Noda as the core engine and the output is converted back to System.DateTime.

Answer 1

I'm not completely sure what you are asking, but here are some tips:

• If all you need is "now" as a UTC DateTime, just use DateTime.UtcNow.

• If you are working with Noda Time instants and need a DateTime, just use instant.ToDateTimeUtc(). There's no point in working with time zones if you just need UTC.

• If you want to validate a DateTime is in UTC, then check the kind:

  dateTime.Kind == DateTimeKind.Utc
  

• Your data layer will probably return DateTimeKind.Unspecified kinds of DateTime, so you would need to first specify the UTC kind before converting to a Noda Time Instant:

  DateTime dt = (DateTime) dataReader["YourDataField"];
  DateTime utc = DateTime.SpecifyKind(dt, DateTimeKind.Utc);
  Instant instant = Instant.FromDateTimeUtc(utc);
  

• Lastly, recognize that UTC isn't a format. It's a time scale. So a value can be "adjusted to UTC", or "of UTC kind", but it can't be "in UTC format".