What is the System.TimeZoneInfo.IsDaylightSavingTi

Question

System.TimeZoneInfo has a method called IsDaylightSavingTime, which takes a DateTime object and returns true if the specified datetime falls in the DST for that timezone. Is there an equivalent function in NodaTime or another way to achieve the same result?

Answer 1

You can get this from a ZoneInterval. Here is an extension method that will help.

public static bool IsDaylightSavingsTime(this ZonedDateTime zonedDateTime)
{
    var instant = zonedDateTime.ToInstant();
    var zoneInterval = zonedDateTime.Zone.GetZoneInterval(instant);
    return zoneInterval.Savings != Offset.Zero;
}

Now you can do:

zdt.IsDaylightSavingsTime();

If you don't have a ZonedDateTime, you can get one from a DateTimeZone plus either an Instant or a LocalDateTime. Or you can massage this extension method to take those as parameters.

Update: This function is now included in Noda Time v1.3 and higher, so you no longer have to write the extension method yourself.