Difference between two ZonedDateTime in Period

Question

Using LocalDate, I got the difference expressed in a Period instance. For example:

LocalDate born = LocalDate.of(1990, Month.SEPTEMBER, 30);
Period myAge = Period.between(born, LocalDate.now());
System.out.println("My age is: "+myAge.getYears()+" years "+myAge.getMonths()+" months "+myAge.getDays()+" days.");

Output:

My age is: 26 years 6 months 23 days

So, I was using period to get the age in years, months and days.

I would like to do the same with ZoneDateTime using two time zones (US/Pacific and Australia/Melbourne). For example:

ZonedDateTime now = ZonedDateTime.now(); // US/Pacific

LocalDate date = LocalDate.of(1990, Month.SEPTEMBER, 30);
LocalTime time = LocalTime.of(23, 55);
ZoneId zone = ZoneId.of("Australia/Melbourne");
ZonedDateTime born = ZonedDateTime.of(date, time, zone);

I would like to get the same output as I got with LocalDate. What should I do? Does it make sense?

Expected output:

My age is: 26 years 6 months 24 days

Answer 1

The first line of Period documentation state that it is a date based amount of time in ISO-8601 format. It is not meant to be used with XXXTime.

However, ZonedDateTime offer you an until method which will return the number of a given ChronoUnit until another Temporal (now in your case).

For example :

born.until(now, ChronoUnit.YEARS);

would return 26.

One trick is to add the difference retrieved to the starting date and then process the next ChronoUnit

For example :

long years = born.until(now, ChronoUnit.YEARS);
born = born.plusYears(years);

long months = born.until(now, ChronoUnit.MONTHS);
born = born.plusMonths(months);

long days = born.until(now, ChronoUnit.DAYS);

And then you can print your variables.