6

I tried to calculate the difference between two dates and I noticed one thing. When calculating only the days, the start of daylight saving time is included in the interval, so the result will be shorter with 1 day.

To obtain accurate results, the value of hours also must be considered.

For example:

SimpleDateFormat format = new SimpleDateFormat("MM-dd-yyyy");
Date dfrom = format.parse("03-29-2015");
Date dto = format.parse("03-30-2015");
long diff = dto.getTime() - dfrom.getTime();
System.out.println(diff);
System.out.println("Days: "+diff / (24 * 60 * 60 * 1000));
System.out.println("Hours: "+diff / (60 * 60 * 1000) % 24);

Output:

82800000
Days: 0
Hours: 23

Does anybody have a better solution?

Tunaki
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tib
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    Can you use java.time (Java 8) or Joda Time instead? Both will make this a *lot* simpler. – Jon Skeet Oct 02 '15 at 10:05
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    Possible duplicate of [Calculating the difference between two Java date instances](http://stackoverflow.com/questions/1555262/calculating-the-difference-between-two-java-date-instances) – Tom Oct 02 '15 at 10:10
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    The root cause is your assumption in line 6 that every day has 24 hours, when you already know that the interval you are measuring contains a day that is only 23 hours long. – Breandán Dalton Oct 02 '15 at 10:35

1 Answers1

11

Oh yes a better solution there is!

Stop using the outmoded java.util.Date class and embrace the power of the java.time API built into Java 8 and later (tutorial). Specifically, the DateTimeFormatter, LocalDate, and ChronoUnit classes.

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM-dd-yyyy");
LocalDate date1 = LocalDate.parse("03-29-2015", formatter);
LocalDate date2 = LocalDate.parse("03-30-2015", formatter);
long days = ChronoUnit.DAYS.between(date1, date2);
System.out.println(days); // prints 1
Tunaki
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