Differences between two dates

Question

Consider the code below. I'm calculating the differences in days between two dates. However, the output is sometimes invalid. Does anyone know how this could be? Don't be concerned about leap years.

SimpleDateFormat myFormat = new SimpleDateFormat("dd-MM-yyyy")           
Date date1 = (Date) myFormat.parse(datenow);
Date date2 = (Date) myFormat.parse(factuurdatumList.get(i));
long difference = date1.getTime() - date2.getTime();
System.out.println("Days: " + TimeUnit.DAYS.convert(difference, TimeUnit.MILLISECONDS));
int openstaand = (int) TimeUnit.DAYS.convert(difference, TimeUnit.MILLISECONDS);

*"output is sometimes invalid"* In what way? Show example. But I'll bet that the invalid output is caused by dates crossing a Daylight Savings Time transition. — Andreas, Jun 23 '18 at 19:38
Please read [How do I ask a question that is answerable?](http://stackoverflow.com/help/how-to-ask) before attempting to ask more questions so you will be better prepared and able to ask a question that will be well received and more importantly **answerable**. — , Jun 23 '18 at 20:25
I recommend you avoid the `SimpleDateFormat` class. It is not only long outdated, it is also notoriously troublesome. Today we have so much better in [`java.time`, the modern Java date and time API](https://docs.oracle.com/javase/tutorial/datetime/). — Ole V.V., Jun 23 '18 at 21:34

score 2 · Answer 1 · edited Jun 24 '18 at 03:42

2

Update: Changed day and month to allow single digit, and added example dates and output.

Easy enough, if you stop using the old out-dated Date class.

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("d-M-uuuu");
LocalDate date1 = LocalDate.parse("23-6-2018", fmt);
LocalDate date2 = LocalDate.parse("23-12-2018", fmt);
long days = ChronoUnit.DAYS.between(date1, date2);
System.out.println("Days: " + days);

Output

Days: 183

See this code run live at IdeOne.com.

edited Jun 24 '18 at 03:42

Basil Bourque

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answered Jun 23 '18 at 19:37

Andreas

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gives DataTimeParseException , it can't parse 23-6-2018 ?? Does only changing it to d-M-uuuu works? In other words, will it also take 23-12 then? – Not Dutch Jun 23 '18 at 20:56
it does not work? – Not Dutch Jun 23 '18 at 21:05
for some reason days return a DATE for me? WTF? – Not Dutch Jun 23 '18 at 21:24
@NotDutch No idea what you're doing. Updated answer to show how it works. – Andreas Jun 23 '18 at 22:44
I see what the problem is. It outputs the days as a negative number:P Which i know is the same for the new class, but if youre calculating stuff with it.. – Not Dutch Jun 23 '18 at 23:00
Used Math.abs and it worked man, thanks:) – Not Dutch Jun 23 '18 at 23:07

Differences between two dates

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