Dates & Times (DateTime)

Dates are deceptively tricky — timezones, leap years, daylight saving, formatting. PHP's DateTimeImmutable handles all of it for you. Learn to create, format, do arithmetic on, and compare dates safely, and you'll never reach for raw timestamp maths again.

Learn Dates & Times (DateTime) in our free PHP course — a beginner-friendly interactive lesson with worked examples, a practice exercise and a quick recall.

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

What You'll Learn in This Lesson

1️⃣ Creating Dates

Build a date by passing a string to new DateTimeImmutable(...) . It accepts ISO dates ( '2026-01-15' ), full timestamps, and even friendly phrases like 'now' , 'next friday' or '+2 weeks' . To turn an object back into text, call format() with format letters .

2️⃣ Formatting with format()

The format string is a recipe of single letters, where case matters : Y is a four-digit year, m a zero-padded month, d a zero-padded day, H:i:s 24-hour time. Any letter you want printed literally must be escaped with a backslash — that's why the ISO example below has \T .

3️⃣ Date Arithmetic

To move a date forwards or backwards, describe the span with a DateInterval and call add() or sub() . The interval string starts with P (period) and uses T before time parts: P10D is ten days, PT2H30M is two and a half hours. For quick phrases, modify('+3 days') is even handier. Because the object is immutable, each call returns a new date and leaves the original alone.

4️⃣ Comparing Dates with diff()

To find the gap between two dates, call $a->diff($b) , which returns a DateInterval you can read or format. Use ->days for the true total number of days, the broken-down ->y/->m/->d for years/months/days, and ->invert (which is 1 ) to tell direction. You can also compare two date objects directly with < , > and == .

5️⃣ Parsing & Timezones

When a string isn't in a standard format — say 18/06/2026 — tell PHP the layout with createFromFormat() . For correct times, attach a DateTimeZone when you build the date, then setTimezone() to convert it for display. Storing in UTC and converting only at render time is the pattern that keeps you out of daylight-saving trouble.

Now you try — fill in each ___ using the 👉 hint, then run it and check against the Output panel.

These lines compute a date one week from a start date — but they're scrambled. Put them in the order that prints 2026-06-25 .

Create the start date ( B ) and the interval ( C ) — order between these two doesn't matter — then add them to get a new date ( D ), and finally format it ( A ). You can't reference $next before it exists.

2026-06-18 — the object is immutable , so modify() returns a new object that was never captured. The original is unchanged. (You'd need $d = $d->modify(...) .)

10 — ->days is the total number of days between the two dates.

3. What does format('jS') output for the 3rd?

3rd — j is the day without a leading zero and S adds the English ordinal suffix.

📋 Quick Reference — Dates

No code is filled in this time — just a brief and an outline. Write it yourself, run it on onecompiler.com/php or your own machine, then check your result against the expected output in the comments.

Practice quiz

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