How Do I Compare The System Time With The Time I've Inputted In C#

using System;
using System.Threading;
    static void Main(string[] args)
    {
      TimeSpan testNow = DateTime.Now.TimeOfDay;  // in real use, this is the now TimeSpan value to use
      // interval all on same day
      testNow = new TimeSpan(12, 0, 0);
      TimesAreInputSoSetupProcessing(10, 15, 14, 30, testNow);   // now is in interval
      testNow = new TimeSpan(9, 0, 0);
      TimesAreInputSoSetupProcessing(10, 15, 14, 30, testNow);   // now is before interval
      testNow = new TimeSpan(20, 0, 0);
      TimesAreInputSoSetupProcessing(10, 15, 14, 30, testNow);   // now is after interval
      // intervals span midnight
      testNow = new TimeSpan(12, 0, 0);
      TimesAreInputSoSetupProcessing(21, 15, 13, 30, testNow);    // now is in interval
      testNow = new TimeSpan(18, 0, 0);
      TimesAreInputSoSetupProcessing(21, 15, 13, 30, testNow);    // now is outside interval
    }
    private static Timer beginTimer;
    private static Timer stopTimer;
    private static readonly TimeSpan OneDay = new TimeSpan(1, 0, 0, 0);  // this SHOULD be static. It'll never change.

    // call this when the user has input the 4 values (Hr and Min) of the two interval endpoints
    static void TimesAreInputSoSetupProcessing(int startHr, int startMin, int endHr, int endMin, TimeSpan now)
    {
      // I'm assuming you've already range-checked the 4 values before you get here!!!!
      // Or you'll add it here.
      TimeSpan startTime = new TimeSpan(startHr, startMin, 0);
      TimeSpan endTime = new TimeSpan(endHr, endMin, 0);
      TimeSpan untilBegin = startTime - now;
      TimeSpan untilStop = endTime - now;
        // check if start to end is all same day
      if (startTime < endTime)
      {
        if (startTime <= now && now < endTime)
        {
          // Already in the specified interval.
          untilBegin = TimeSpan.Zero;
        }
      }
      else if (now < endTime || startTime <= now) // spans midnight
      {
        // Already in the specified interval.
        untilBegin = TimeSpan.Zero;
      }

      // either end of the interval might be tomorrow!
      if (untilBegin < TimeSpan.Zero)
        untilBegin += OneDay;
      if (untilStop < TimeSpan.Zero)
        untilStop += OneDay;
      Console.WriteLine("startTime: {0}, endTime: {1}, now: {2}", startTime, endTime, now);
      Console.WriteLine("untilBegin: {0}", untilBegin);
      Console.WriteLine("untilStop: {0}", untilStop);
      //NOTE: the Timer creation is commented out for testing the untilXXX calculations
      //beginTimer = new Timer(BeginSomething, null, untilBegin, OneDay);
      //stopTimer = new Timer(StopSomething, null, untilStop, OneDay);
    }
    static void BeginSomething(object state)
    {
      // here is where you begin whatever processing you want to be done during the interval
    }
    static void StopSomething(object state)
    {
      // here is where you end the processing for today
    }