Trigger events on specific time in datetime

My game contains a datetime to represent the in-game date, and it will forward the time automatically. And I have a series of events that will only occurs on a specific date.

Question is what is the best way so that when the time comes it will trigger these events?

Now the best I can think of is setting a date for each of these events, so everytime when the game time is updated, I check if (game time >= event time). But it seems to drain resources quite much because the time is updated very frequently per second. Is there any better way to do this?

Here is my DateManager:

 public class DateTimeManager : MonoBehaviour
 {
     //Singleton
     public static DateTimeManager dateManager;
 
     //Get other objects
     private GameStatManager gameStatManager;
 
     //Local var
     private Text displayTime;
     private Text displayDate;
     private Image timeScaleImage;
     float counter;
     int dayCounter;
 
     //Get speed icon
     public Sprite slow;
     public Sprite medium;
     public Sprite fast;
 
     //Output var
     public DateTime dateTime;
 
     void Start(){
 
         //Singleton
         dateManager = this;
 
         //Get other objects
         gameStatManager = GameObject.Find("GameStatManager").GetComponent<GameStatManager>();
         displayDate = transform.Find("Date").gameObject.GetComponent<Text>();
         displayTime = transform.Find("Time").gameObject.GetComponent<Text>();
         timeScaleImage = transform.Find("TimeScale").gameObject.GetComponent<Image>();
 
         //Initialize
         dateTime = gameStatManager.GetDateTime();
 
         //Set default
         Time.timeScale = 1;
         timeScaleImage.sprite = slow;
         counter = 0f; 
         dayCounter = 0;
     }
 
     void Update()
     {
         counter += Time.deltaTime;
 
         if (counter >= 1f / Time.timeScale){
             counter -= 1f / Time.timeScale;
 
             //Add 10 muinutes
             dateTime = dateTime.AddMinutes(10);
 
             //Add dayCounter
             dayCounter++;
             if(dayCounter >= 144){
                 dayCounter = 0;
                 gameStatManager.AddTotalDay();
             }
 
             //Display datetime
             displayDate.text = dateTime.ToString("dd MMM, yyyy");
             displayTime.text = dateTime.ToString("h:mmtt");  
 
             //To GSM
             gameStatManager.SetDateTime(dateTime);
         }
     }