Date difference calculation

Question

Hello Everyone,
We need to calculate a day difference between two days. There is many suggestions about using the following approach:
(date1.getTime() - date2.getTime())/86400000.
This seems to work until we hit a Daylight Savings Time issue and nobody seems to talk about that. When in April, for example, we get 1 hour less then the result of the calculation above will not be the whole number. Well, we can use Math.ceil() function for that. Then, in October, we get 1 hour back so now we have to use Math.floor() function to get the right result.
Does anybody have any idea as to when to use one or another. I was thinking of using modulus division. If the result is not equal to zero then we have to apply one of those functions. The question now is, how to identify which function to apply? Or is there any other, less cumbersome way to properly get day difference between two dates?
Any help will be greatly appreciated.
Thanks,
Yourii

Answer 1

I think i figured out how to calculate the difference in days with Daylight Savings Time changes. Here is the code:
     * This method returns difference in days between two Dates passed in.
     * It identifies Daylight Savings Time changes and automatically
     * adds or substracts one hour when needed ...
     private int dayDifference(java.util.Date date1, java.util.Date date2) {
     final long M_SECS_PER_DAY = 24*60*60*1000;
     final long M_SECS_PER_HOUR = 60*60*1000;
     long days = (date1.getTime() - date2.getTime());     
     if (days%M_SECS_PER_DAY != 0) {
     if ((days + M_SECS_PER_HOUR)%M_SECS_PER_DAY == 0) {
     System.out.println("Adding one hour ...");
     days += M_SECS_PER_HOUR;
     } else {
     System.out.println("Substracting one hour ...");
     days -= M_SECS_PER_HOUR;
     } else {
     System.out.println("No alterations made ...");
     return (int)(days / M_SECS_PER_DAY);
Let me know what you think ...