using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace testrundo1
{
    class Program
    {
        static void Main(string[] args)
        {
            var openTime = DateTime.Parse("11:00 AM");
            var closeTime = DateTime.Parse("10:00 PM");
            var lunchTime = DateTime.Parse("3:00 PM");
            Console.WriteLine(DateTime.Now);
            Console.WriteLine(openTime);
            if (openTime < DateTime.Now && DateTime.Now < lunchTime)
                Console.WriteLine("Lunch time!");
            else if
                (DateTime.Now > lunchTime && DateTime.Now < closeTime)
                Console.WriteLine("Dinner time!");
            else
                Console.WriteLine("Bummer");

            Console.ReadLine();
        }
    }
}

Business will open in (insert hour until opens) hour and (insert minutes until opens) minutes.
a] If now is < 11:00 AM
b] if now is > 10:00 PM (till next day 11:00 AM)