Why ChronoUnit.HOURS.between() is NOT working?

Question

I was trying to get the hours between two local dates. And I used the code below :

 LocalDate startDate =  LocalDate.of(2000, 4, 30);

    long noOfHours = startDate.until(LocalTime.now(), ChronoUnit.HOURS);
    
    System.out.println(noOfHours);

I am having the error below :

Exception in thread "main" java.time.DateTimeException: Unable to obtain LocalDate from TemporalAccessor: 13:44:53.095819600 of type java.time.LocalTime
    at java.base/java.time.LocalDate.from(LocalDate.java:397)
    at java.base/java.time.LocalDate.until(LocalDate.java:1645)
    at BirthDay.App.main(App.java:36)

Answer 1

Error 1

As the exception states : you need coherent bound values, LocalTime has no day/month/year composants to be compared to a LocalDate

LocalDate startDate = LocalDate.of(2000, 4, 30);
long noOfHours = startDate.until(LocalTime.now(), ChronoUnit.HOURS);
// >> DateTimeException: Unable to obtain LocalDate from java.time.LocalTime

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Error 2

Also you need composants that have the unit required by your ChronoUnit, using 2 LocalDate won't work with HOURS as they have none.

LocalDate startDate = LocalDate.of(2000, 4, 30);
long noOfHours = startDate.until(LocalDate.now(), ChronoUnit.HOURS);
// >> UnsupportedTemporalTypeException: Unsupported unit: Hours

---

Use LocalDateTime for that, to be coherent for both bounds and for unit time

LocalDateTime startDate = LocalDateTime.of(2000, 4, 30, 0, 0, 0);
long noOfHours = startDate.until(LocalDateTime.now(), ChronoUnit.HOURS);
System.out.println(noOfHours); // 185793