Date and Time API

Definition

The java.time package (Java 8) replaced the old Date and Calendar. Its classes, such as LocalDate, LocalDateTime, Duration and Period, are immutable and clear, and they handle months, days and formatting correctly.

Example code

Adding months, measuring days and formatting a date

import java.time.LocalDate;
import java.time.Period;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;

class Demo {
    public static void main(String[] args) {
        LocalDate start = LocalDate.of(2026, 1, 31);

        System.out.println(start.plusMonths(1));                       // 2026-02-28: month-end is handled
        System.out.println(start.getDayOfWeek());

        LocalDate end = LocalDate.of(2026, 12, 25);
        System.out.println(ChronoUnit.DAYS.between(start, end) + " days");
        System.out.println(Period.between(start, end));

        System.out.println(start.format(DateTimeFormatter.ofPattern("dd MMM yyyy")));
    }
}

// Output:
// 2026-02-28
// SATURDAY
// 328 days
// P10M25D
// 31 Jan 2026