Understanding PHP Function Date Timezone Version Get

The timezone_version_get() function returns the version of the timezone database bundled with the intl extension. The timezone database (commonly called the tz database or IANA tz data) is the canonical source of the world's timezone rules — UTC offsets, daylight-saving transitions, and historical changes. Governments change these rules regularly, so the database is revised several times a year and tagged with a version like 2024.1.

Knowing the version matters because out-of-date rules produce wrong times. If a country shifts its DST start date and your server still ships an old database, every date calculation across that transition is off by an hour. timezone_version_get() lets you read which version PHP is actually using so you can audit it, log it, or warn when it is stale.

This page covers the syntax, how to call it safely, how to read the result, and how it relates to the other PHP timezone functions.

Syntax

The timezone_version_get() function has a very simple syntax. Here is the syntax:

The syntax of PHP timezone_version_get() function

string timezone_version_get ( void )

Available since PHP 5.2.0.

This function takes no arguments and returns a string holding only the version number, such as 2023.3 or 2024.1. The format is YYYY.N — the four-digit year of the IANA release followed by the sequential release within that year (a, b, c… in IANA become .1, .2, .3 here).

Note: timezone_version_get() is part of the intl extension, not the core date/time extension. It reports the bundled intl/ICU copy of the timezone data, which can differ from the version PHP's DateTime/DateTimeZone classes use. To check whether the intl extension is present at all, use extension_loaded('intl') before calling it.

Usage

A typical call looks like this:

1. Guard with extension_loaded('intl') so the script does not fatal on servers without the extension.
2. Call timezone_version_get() to retrieve the version string.
3. Store, log, or display the value — or compare it against a minimum you expect.

Example

Here is an example code snippet that shows how to use the timezone_version_get() function in your PHP applications:

Example of timezone_version_get() function in PHP

Note: This function requires the intl extension. If the extension is not enabled, the function will not be available. The example above includes a check to prevent a fatal error.

Warning when the database is stale

Because the version is just a YYYY.N string, you can compare it against a minimum you trust. This is handy for a health-check endpoint or a deployment guard:

<?php
$minimum = '2024.1';
$current = timezone_version_get();

if (version_compare($current, $minimum, '<')) {
    echo "Warning: timezone database $current is older than $minimum. Update the intl/ICU library.";
} else {
    echo "Timezone database $current is up to date.";
}
?>

version_compare() treats the dotted version like a software version, so 2024.1 correctly compares as newer than 2023.3.

Related functions

timezone_version_get() is the only function that reports the database version. The rest of PHP's timezone toolkit works with the data itself:

• date_default_timezone_set() and date_default_timezone_get() — set and read the default timezone used by every date function.
• timezone_identifiers_list() — list every supported timezone identifier (e.g. Europe/London).
• timezone_name_get() — get the name of a DateTimeZone object.
• timezone_abbreviations_list() — map abbreviations like CET to their offsets.

Conclusion

timezone_version_get() is a small but practical function: it tells you exactly which IANA timezone database the intl extension is using. Always guard the call with extension_loaded('intl'), and consider comparing the returned version against a known-good minimum so stale timezone rules surface during deployment rather than as wrong timestamps in production.

Practice