Dates & Times (LocalDate, LocalDateTime)

Dates look simple and turn out to be a minefield — leap years, month lengths, time zones. Java's modern java.time package handles all of it with clean, immutable classes. This lesson covers the three you'll use daily: LocalDate , LocalTime , and LocalDateTime .

Learn Dates & Times (LocalDate, LocalDateTime) in our free Java course — a beginner-friendly interactive lesson with worked examples, a practice exercise and…

Part of the free Java course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

You'll need comfort with method calls and imports — everything here lives in java.time . Knowing that objects can be immutable will make the key idea click instantly.

💡 Analogy: A LocalDate is like a single page torn from a calendar — it says "17 June 2026" and nothing else. You can't erase and rewrite it; if you want "one week later" you grab a fresh page. That's immutability: every plusDays hands you a new page and leaves the original exactly as it was. This is what makes java.time safe to pass around without anyone secretly changing your dates.

There are three everyday building blocks: LocalDate (date only), LocalTime (time only), and LocalDateTime (both). "Local" means no time zone — perfect for birthdays, opening hours, and appointments where the zone is understood. We'll stick to these three.

Use the static of(...) factory methods to build a specific value, or now() for the current moment. Months are 1-based here (June is 6) — a welcome fix from the old Date class where January was 0. You can also use the readable Month.JUNE enum.

Once you have an object, getters pull out the pieces: getYear() , getMonth() , getDayOfMonth() , getDayOfWeek() , and more.

Every java.time object is immutable . A method like plusDays(10) does not change the date — it returns a brand-new date and leaves the original untouched. This is wonderful for safety but trips up everyone at least once.

Compare two dates with isBefore , isAfter , and isEqual . To measure the gap, you have two tools:

DateTimeFormatter converts in both directions: format turns a date object into a custom String, and parse turns a String back into a date object. You define the shape with a pattern of letters.

These lines compute and print how many days remain until a holiday. They've been shuffled.

Create both dates first, measure the gap with ChronoUnit.DAYS.between (earlier date first so the result is positive), then print.

Predict the output before opening each answer.

Answer: 2026-06-17 — unchanged. plusDays(5) returns a new date that is thrown away because the result isn't captured. LocalDate is immutable. To move the date you'd need d = d.plusDays(5); .

Answer: 2026-02-28 . There's no 31 February, so plusMonths clamps to the last valid day of the target month. (2026 isn't a leap year, so February ends on the 28th.) java.time handles month-length edge cases for you.

Answer: 16 . between counts whole days from start to end — June 17 minus June 1 is 16 days. It's exclusive of the start and inclusive of the end's calendar position, so the gap, not the number of dates, is 16.

🎯 Your Turn #1 — 18th birthday

Given a birth date, compute and print the 18th-birthday date.

🎯 Your Turn #2 — Countdown

Count the days between today and a deadline using ChronoUnit .

🧩 Mini-Challenge — Age calculator

Write an age method that returns whole years between a birth date and today using Period .

You can now build dates and times with java.time , you understand why every object is immutable (and the bug that causes), and you can add, compare, measure, format, and parse with confidence. You're using the same modern API every professional Java codebase relies on.

Next up: Comparable & Comparator — teaching Java how to sort your own objects.

Practice quiz

• Browse all free courses
• Cheat sheets & quizzes
• Coding dictionary