There are times when we need to calculate the difference between two dates.

For example:
There was requirement in a project on ticket reservation system to restrict the reservation of ticket to employees who have been hired for at least 6 months. In such cases we need to calculate the difference between two dates..
Below is an example code in java to calculate the difference between two dates:

import java.util.Calendar;
 
public class DateDiffExample
{  
    public static void main(String[] args)
   {
                long diffInMillisec=0;
                long diffInDays=0;
               Calendar firstDate =null;
               Calendar secondDate =null;
                try{
                         // Create two calendars instances
                         firstDate = Calendar.getInstance();
                         secondDate = Calendar.getInstance();
                      
                        //Set the dates
                        firstDate.set(2009, 8, 1);       
                        secondDate.set(2009, 7, 31);
 
                        // Get the difference between two dates in milliseconds    
                       diffInMillisec = firstDate.getTimeInMillis() - secondDate.getTimeInMillis();     
 
                       // Get difference between two dates in days
                       diffInDays = diffInMillisec / (24 * 60 * 60 * 1000);       
 
                    }catch(Exception ex)
                    {
                                ex.printStackTrace();
                     }             
           }
 }