Solved

How to calculate the number of days between two Dates?

Posted on 2009-05-07
8
1,873 Views
Last Modified: 2012-05-06
I'm trying to write a function that will calculate the number of days that exist between two dates,  but have been unable to come up with an adequete solution thus far. In the reasearch that I've done, I've seen some methods convert the dates to milliseconds, subtract, then convert back. In others, they've incrimented a count variable, and simple added days to the earlier date until the two dates matched. Unfortunately, neither of these methods seems completely accurate under all conditions, nor do they seem as elegant as you'd hope them to be.

How have you done this calculation before? Is there a common library or standard function that's commonly used for this calculation?

Thanks in advance.
0
Comment
Question by:MehtaJasmin
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
  • 2
  • +1
8 Comments
 
LVL 86

Expert Comment

by:CEHJ
ID: 24324928
0
 
LVL 16

Expert Comment

by:CuteBug
ID: 24324931
0
 
LVL 92

Expert Comment

by:objects
ID: 24332244
the problem is more in the definition of what you mean by the number of days between two dates. Once that is defined then implementation is generally straight forward. Using a Calendar for the arithmetic is the standard way, and there are also libraries around.

So what is your definition of the number of days between 2 dates?

0
Instantly Create Instructional Tutorials

Contextual Guidance at the moment of need helps your employees adopt to new software or processes instantly. Boost knowledge retention and employee engagement step-by-step with one easy solution.

 

Author Comment

by:MehtaJasmin
ID: 24335002
My requirement is, if I pass dateA and dateB to the some java method /  API, it should return me how many days they are apart. It should consider if they in the same year/leap year etc. Basically I am coding for password expiry logic where I need to check that last time user has updated password, has it been 60 days yet. If current date is exceeding the 60 day period of validity then I need to prompt user to change the password.

I have dig in to java.util.Calendar API but could not find appropriate method. Also tried writing test program using DateUtils of commons package with getFragmentInDays() and iterator(java.util.Calendar focus,  int rangeStyle). But looks like I need to write quite a bit of math around iterator() to get the result out. So I was looking for any straight api / jar available for my need.

Hope this defines the question better.

Hope this clears the question.
0
 
LVL 92

Accepted Solution

by:
objects earned 250 total points
ID: 24335051
Easiest way to do that is as well (or instead of) storing the last updated date, you store the expiry date. Then you just have to check if the current date is after the expiry date.
And if you don't store it you can just use the Calendar class to add the 60 day period to the last updated date and then compare with current date. Much simpler that calculating differences which is messy.

http://helpdesk.objects.com.au/java/how-do-i-add-a-specified-number-of-hours-to-a-java-date

(Use Calendar.DATE instead of Calendar.HOUR  to add days)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 24335080
For your two Date instances:
final int TIME_OUT_DURATION = 1000 * 60 * 60 * 24 * 60;
boolean needToChangePassword = (d1.getTime() - d2.getTime()) > TIME_OUT_DURATION;

Open in new window

0
 

Author Closing Comment

by:MehtaJasmin
ID: 31580092
Thanks! Actually had the same idea about the time you posted it. It's a much easier solution to our exact situation than attempting to calculate the time between two arbitrary dates. Thanks again!
0
 
LVL 92

Expert Comment

by:objects
ID: 24353273
thanks mate, let me know if you need any other help.

0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
hibernate example using maven 12 82
ejb on wildfly 5 48
servlet and mdb, jms error 1 57
dao vs facade design patterns 2 38
INTRODUCTION Working with files is a moderately common task in Java.  For most projects hard coding the file names, using parameters in configuration files, or using command-line arguments is sufficient.   However, when your application has vi…
Java contains several comparison operators (e.g., <, <=, >, >=, ==, !=) that allow you to compare primitive values. However, these operators cannot be used to compare the contents of objects. Interface Comparable is used to allow objects of a cl…
Viewers will learn about basic arrays, how to declare them, and how to use them. Introduction and definition: Declare an array and cover the syntax of declaring them: Initialize every index in the created array: Example/Features of a basic arr…
The viewer will learn how to implement Singleton Design Pattern in Java.

726 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question