PHP Date and Time

Date & Time Handling in PHP (DateTime Class & date())

PHP provides robust date and time manipulation capabilities through procedural functions (like date(), strtotime(), time()) and the modern object-oriented DateTime, DateTimeImmutable, and DateInterval classes.

Procedural vs Object-Oriented Date API

Date Format Tokens

• Y: 4-digit year (2026).
• m: 2-digit month with leading zero (01 through 12).
• d: 2-digit day of month with leading zero (01 through 31).
• H: 24-hour hour format (00 through 23).
• i: Minutes (00 through 59).
• s: Seconds (00 through 59).

flowchart TD
    A["Create Date Object"] --> B["new DateTimeImmutable('now', new DateTimeZone('UTC'))"]
    B --> C["Format Output: $dt->format('Y-m-d H:i:s')"]
    B --> D["Date Arithmetic: $dt->modify('+30 days')"]
    B --> E["Timezone Shift: $dt->setTimezone(new DateTimeZone('Asia/Dhaka'))"]

Practical Code Example

<?php
declare(strict_types=1);

// Set default fallback timezone
date_default_timezone_set('UTC');

// 1. Procedural Date Formatting
$currentTimestamp = time();
$formattedDate = date('Y-m-d H:i:s', $currentTimestamp);

// 2. Modern OOP DateTimeImmutable Usage
$now = new DateTimeImmutable('now', new DateTimeZone('UTC'));
$futureExpiration = $now->modify('+30 days');

// Timezone Conversion
$dhakaZone = new DateTimeZone('Asia/Dhaka');
$localTime = $now->setTimezone($dhakaZone);

echo "UTC Timestamp: " . $now->format('Y-m-d H:i:s T') . "
";
echo "Dhaka Local Time: " . $localTime->format('Y-m-d H:i:s T') . "
";
echo "Expiration Date (+30d): " . $futureExpiration->format('F j, Y') . "
";

Best Practices

• Prefer DateTimeImmutable over DateTime: DateTimeImmutable methods return new instances when modified, preventing unexpected side-effect mutations.
• Store Timestamps in UTC in Databases: Always record database timestamps in UTC (+00:00) and convert to local timezones during user presentation.
• Always Explicitly Set Timezone: Set date.timezone in php.ini or call date_default_timezone_set() at application bootstrapping.

Self-Check Challenge

Create a DateTimeImmutable object for today's date, add 7 days using modify('+7 days'), and output it formatted as Y-m-d!