NodaTime – time offsets C#

using NodaTime;
using NodaTime.TimeZones;

namespace NodaTimeLibrary.Classes;
/// <summary>
///
/// Patterns for Offset values
/// https://nodatime.org/3.1.x/userguide/offset-patterns
///
/// Time zone list
/// https://nodatime.org/TimeZones
/// https://gist.github.com/jrolstad/5ca7d78dbfe182d7c1be
/// </summary>
internal static class TimeOperations
{
    /// <summary>
    /// Gets the time zone offset and whether daylight savings is in effect for the specified time zone and UTC date and time.
    /// </summary>
    /// <param name="timeZoneId">The identifier of the time zone.</param>
    /// <param name="dateTimeUtc">The UTC date and time.</param>
    /// <returns>A tuple containing the time zone offset as a string and a boolean indicating whether daylight savings is in effect.</returns>
    public static (string offset, bool daylightSavings) TimeZoneOffset(string timeZoneId, DateTime dateTimeUtc)
    {

        Instant instant = Instant.FromDateTimeUtc(dateTimeUtc);
        DateTimeZone zone = DateTimeZoneProviders.Tzdb[timeZoneId];

        ZonedDateTime dateTime = new(instant, zone);
        var daylightSavings = dateTime.IsDaylightSavingsTime();

        Offset offset = daylightSavings ? zone.MinOffset : zone.MaxOffset;

        return (offset.ToString("m", null), daylightSavings);
    }

    /// <summary>
    /// Determines whether the specified date and time is during daylight saving time in the given time zone.
    /// </summary>
    /// <param name="zonedDateTime">The date and time to check.</param>
    /// <returns>True if the specified date and time is during daylight saving time; otherwise, false.</returns>
    public static bool IsDaylightSavingsTime(this ZonedDateTime zonedDateTime)
    {
        var instant = zonedDateTime.ToInstant();
        var zoneInterval = zonedDateTime.Zone.GetZoneInterval(instant);
        return zoneInterval.Savings != Offset.Zero;
    }

    /// <summary>
    /// Gets the current system date and time in the specified time zone.
    /// </summary>
    /// <param name="zone">The time zone identifier. Default is "US/Pacific".</param>
    /// <returns>The current system date and time in the specified time zone.</returns>
    public static DateTime GetSysDateTimeNow(string zone = "US/Pacific")
    {
        Instant now = SystemClock.Instance.GetCurrentInstant();
        return now.InZone(DateTimeZoneProviders.Tzdb[zone]).ToDateTimeUnspecified();
    }

    /// <summary>
    /// Gets all the time zones for a given country code.
    /// </summary>
    /// <param name="countryCode">The country code. Default is "US".</param>
    /// <returns>A list of TzdbZoneLocation objects representing the time zones.</returns>
    public static List<TzdbZoneLocation> GetAllTimeZones(string countryCode = "US") =>
        (TzdbDateTimeZoneSource.Default.ZoneLocations ?? Enumerable.Empty<TzdbZoneLocation>().ToList())
        .Where(x => x.CountryCode == countryCode)
        .ToList();
}

using NodaTimeLibrary.Classes;

namespace NodaTimeLibrary.Models;

/// <summary>
/// Represents the East Coast time zone.
/// </summary>
public class EastCoast
{
    private string _timeZoneId => "US/Eastern";

    /// <summary>
    /// Gets the offset of the East Coast time zone.
    /// </summary>
    /// <returns>The offset of the East Coast time zone.</returns>
    public string Offset =>
        TimeOperations.TimeZoneOffset(_timeZoneId, 
            DateTime.SpecifyKind(TimeOperations.GetSysDateTimeNow(_timeZoneId), 
                DateTimeKind.Utc)).offset;

    /// <summary>
    /// Determines whether the East Coast time zone is currently in daylight saving time.
    /// </summary>
    /// <returns>True if the East Coast time zone is currently in daylight saving time; otherwise, false.</returns>
    public bool DaylightSavingsSupported =>
        TimeOperations.TimeZoneOffset(_timeZoneId, 
            DateTime.SpecifyKind(TimeOperations.GetSysDateTimeNow(_timeZoneId), 
                DateTimeKind.Utc)).daylightSavings;
}

using NodaTimeLibrary.Classes;

namespace NodaTimeLibrary.Models;

public class WestCoast
{
    private string _timeZoneId => "US/Pacific";

    /// <summary>
    /// Gets the offset of the West Coast time zone.
    /// </summary>
    /// <returns>The offset of the West Coast time zone.</returns>
    public string Offset =>
        TimeOperations.TimeZoneOffset(_timeZoneId, 
            DateTime.SpecifyKind(TimeOperations.GetSysDateTimeNow(), 
                DateTimeKind.Utc)).offset;

    /// <summary>
    /// Determines whether the West Coast time zone is currently in daylight saving time.
    /// </summary>
    /// <returns>True if the West Coast time zone is currently in daylight saving time; otherwise, false.</returns>
    public bool DaylightSavingsSupported =>
        TimeOperations.TimeZoneOffset(_timeZoneId, 
            DateTime.SpecifyKind(TimeOperations.GetSysDateTimeNow(_timeZoneId), 
                DateTimeKind.Utc)).daylightSavings;
}

namespace NodaTimeLibrary.Models;

/// <summary>
/// Represents the United States with its East Coast and West Coast time zones.
/// </summary>
public class UnitedStates
{
    /// <summary>
    /// Gets or sets the East Coast time zone.
    /// </summary>  
    public EastCoast EastCoast { get; init; } = new();

    /// <summary>
    /// Gets or sets the West Coast time zone.
    /// </summary>
    public WestCoast WestCoast { get; init; } = new();
}

UnitedStates us = new();
AnsiConsole.MarkupLine($"[yellow]United States[/]");
AnsiConsole.MarkupLine($"[cyan]  Eastern offset[/]: [b]{us.EastCoast.Offset}[/]");
AnsiConsole.MarkupLine($"[cyan]Daylight savings:[/] [b]{us.EastCoast.DaylightSavingsSupported.ToYesNo()}[/]");

AnsiConsole.MarkupLine($"[cyan]  Western offset[/]: [b]{us.WestCoast.Offset}[/]");
AnsiConsole.MarkupLine($"[cyan]Daylight savings:[/] [b]{us.WestCoast.DaylightSavingsSupported.ToYesNo()}[/]");

using NodaTime;

namespace NodaTimeLibrary.Classes;
public class PeriodOperations
{
    /// <summary>
    /// Calculates the period between a birthdate and a given date in years, months, and days.
    /// </summary>
    /// <param name="birthDate">The birthdate.</param>
    /// <param name="date">The date to calculate the period to.</param>
    /// <returns>The period between the birthdate and the given date.</returns>
    public static Period YearsOld(DateOnly birthDate, DateOnly date) =>
        Period.Between(LocalDate.FromDateOnly(birthDate), LocalDate.FromDateOnly(date),
            PeriodUnits.Years |
            PeriodUnits.Months |
            PeriodUnits.Days);
}