获取两个日期之间的天数

Question

I use java.time.Period#getDays() to get the number of days for a given period of LocalDate s.

It seems to work for most cases, but for a whole month, I get a period of zero days.

The following test case fails ( java.lang.AssertionError: expected:<30> but was:<0> ):

@Test
public void testOneMonthPeriodDays() {
    Period p = Period.between(LocalDate.of(2017, 06, 01), LocalDate.of(2017, 07, 01));
    assertEquals(30, p.getDays());
}

Answer 1

I believe this is the correct result. If you run the following test you will see that getMonths() returns 1. It seems that getDays is not get the total days but get the remainder days.

@Test
public void testOneMonthPeriodDays() {
    Period p = Period.between(LocalDate.of(2017, 06, 01), LocalDate.of(2017, 07, 01));
    assertEquals(0, p.getDays());
    assertEquals(1, p.getMonths());
}

To get the total number of days between two dates see this question Calculate days between two dates in Java 8

To quote the answer given in that question:

LocalDate dateBefore;
LocalDate dateAfter;
long daysBetween = DAYS.between(dateBefore, dateAfter);

Note that DAYS is member of java.time.temporal.ChronoUnit enum.

Answer 2

JavaDoc for java.time.Period#getDays() says:

returns the amount of days of this period, may be negative

I guess this is missleading and it does not really return the total amount of days.

I use now

final long daysElapsed = ChronoUnit.DAYS.between(LocalDate.of(2017, 06, 01), LocalDate.of(2017, 07, 01));

which works as expected.

Answer 3

Do the following:

long daysDifference = DAYS.between(dayInitial, dayAfter);

where:

LocalDate dateInitial;   //initial date
LocalDate dateAfter;      //later date