Shipment.cs

public interface IDeliveryTimingPolicy
{
    bool IsLate(Shipment shipment);
}

public class StandardDeliveryTiming : IDeliveryTimingPolicy
{
    private readonly DateTime _now;

    public StandardDeliveryTiming(DateTime now)
    {
        _now = now;
    }

    public bool IsLate(Shipment shipment)
    {
        return _now > shipment.DeliveryDate;
    }
}

public class BufferDeliveryTiming : IDeliveryTimingPolicy
{
    private readonly DateTime _now;
    private readonly TimeSpan _buffer;

    public BufferDeliveryTiming(DateTime now, TimeSpan buffer)
    {
        _now = now;
        _buffer = buffer;
    }

    public bool IsLate(Shipment shipment)
    {
        return _now > shipment.DeliveryDate.Add(_buffer);
    }
}

public class Shipment
{
    public required DateTime DeliveryDate { get; init; }
    
    public bool IsLate(IDeliveryTimingPolicy policy)
    {
        return policy.IsLate(this);
    }
}