using System;

public class Program

{

    public static void Main()

    {

        var now = DateTimeOffset.UtcNow;

​

        var utc = TimeZoneInfo.Utc;

        var hawaii = TimeZoneInfo.FindSystemTimeZoneById("Pacific/Honolulu");

        var christmasIslands = TimeZoneInfo.FindSystemTimeZoneById("Pacific/Enderbury");

​

        Console.WriteLine("DateTimeOffset to DateOnly:");

​

        Console.WriteLine($"UTC Now: {now}");

        Console.WriteLine($"Date in Hawaii: {now.ToDateOnly(hawaii)}");

        Console.WriteLine($"Date In Christmas Islands: {now.ToDateOnly(christmasIslands)}");

​

        Console.WriteLine("====================\n");

        Console.WriteLine("DateOnly to DateTimeOffset");

​

        var totallyRandomDate = DateOnly.Parse("2020-03-11");

        Console.WriteLine($"DateTimeOffset UTC: {totallyRandomDate.ToDateTimeOffset(utc)}");

        Console.WriteLine($"DateTimeOffset Hawaii: {totallyRandomDate.ToDateTimeOffset(hawaii)}");

        Console.WriteLine($"DateTimeOffset Christmas Islands: {totallyRandomDate.ToDateTimeOffset(christmasIslands)}");

    }

}

​

public static class DateOnlyExtensions {

    public static DateTimeOffset ToDateTimeOffset(this DateOnly dateOnly, TimeZoneInfo zone) {

        var dateTime = dateOnly.ToDateTime(new TimeOnly(0));

        return new DateTimeOffset(dateTime, zone.GetUtcOffset(dateTime));

    }

​

    public static DateOnly ToDateOnly(this DateTimeOffset dto, TimeZoneInfo zone) {

        var inTargetZone = TimeZoneInfo.ConvertTime(dto, zone);

​

        return DateOnly.FromDateTime(inTargetZone.Date);

    }

}