java.time.Period is a class that represents a quantity or amount of time in terms of years, months, and days. Here’s a brief guide on how to use it:

1. Creating a Period instance

The Period class provides several static methods named of() and between() to create an instance. To create Period of 1 year, 2 months, and 3 days:

Period period = Period.of(1, 2, 3);

Or you can create a Period using LocalDate:

LocalDate start = LocalDate.of(2020, Month.JANUARY, 1);
LocalDate end = LocalDate.of(2023, Month.MARCH, 31);
Period period = Period.between(start, end);

2. Retrieving Years, Months, and Days

Use the getDays(), getMonths(), and getYears() methods to get the number of days, months, and years in the Period.

int days = period.getDays();
int months = period.getMonths();
int years = period.getYears();

3. Adding/subtracting Period to/from a LocalDate

The LocalDate.plus() or LocalDate.minus() methods can be used to add or subtract a Period from a LocalDate.

LocalDate ld = LocalDate.of(2021, Month.JULY, 1);
Period period = Period.of(1, 2, 3);
LocalDate newDate = ld.plus(period);

In this case, newDate will be 1 year, 2 months, and 3 days after July 1, 2021.

4. Mixing units of time

You can use plusDays(), plusMonths(), or plusYears() to add to a Period.

Period period = Period.of(1, 2, 3);
Period newPeriod = period.plusDays(10);

The newPeriod will then be 1 year, 2 months, and 13 days.