title: Show alert popup 5 mins before a specific time
body: <p>Currently i am developing and an Schedule appointment module and in that there is an feature to show an alert to the user 5 mins before appointment time , for example the appointment is scheduled @5pm today then the user should be notified with the alert or popup @4:55 pm that the meeting is due in 5 mins.</p>
  
  <p>I am using PHP and javascript for this project and True Vault to save the data in database which is in No - Sql ,</p>
  
  <p>So just needed to know what is the best way to achieve this without using the cronjobs or features similar to that.</p>
  
  <p>Thanks for any kind of help... </p>