PHP IntlCalendar::set() Method: Usage and Examples

When you need to set one or more calendar fields, it helps to understand both the normal result and what changes with different inputs. This guide focuses on practical examples rather than repeating PHP background material.

IntlCalendar::set provides the behavior described below. IntlCalendar represents a locale-aware ICU calendar. Month indexes are zero-based, while epoch time uses milliseconds.

What Is IntlCalendar::set in PHP?

Set one or more calendar fields. IntlCalendar represents a locale-aware ICU calendar. Month indexes are zero-based, while epoch time uses milliseconds.

Its syntax is:

$calendar->set(...)

Parameters and return value: Read the argument names and optional values in the signature above. Methods use an existing object, while stand-alone functions take direct arguments. The examples demonstrate the relevant arguments and the value returned or the object modified.

Important: When using year/month/day overload, the month is zero-based; leniency may normalize invalid dates.

Example 1: Basic Usage

This first example demonstrates how to set one or more calendar fields with a small input.

<?php

$calendar = IntlCalendar::createInstance("UTC", "en_US");
$calendar->set(IntlCalendar::FIELD_YEAR, 2030);
echo $calendar->get(IntlCalendar::FIELD_YEAR);

The example uses the simplest useful form. IntlCalendar represents a locale-aware ICU calendar. Month indexes are zero-based, while epoch time uses milliseconds. The output may depend on the active ICU locale, PHP configuration, or input supplied to the function.

Example 2: Another Case

Here the input or option changes, making it easier to see where the behavior differs. When using year/month/day overload, the month is zero-based; leniency may normalize invalid dates.

<?php

$calendar = IntlCalendar::createInstance("UTC", "en_US");
$calendar->set(2026, 9, 16);
echo $calendar->get(IntlCalendar::FIELD_DAY_OF_MONTH);

Compare the result to the first example. DateTimeImmutable is often simpler for Gregorian dates; IntlCalendar is useful for ICU calendar systems.

Practical Example: Applying the Function

This standalone example shows how the same operation fits into a small application task. The intl extension is required for this example.

<?php

$calendar = IntlCalendar::createInstance("UTC", "en_US");
$calendar->set(2026, 0, 15, 9, 30);
echo $calendar->get(IntlCalendar::FIELD_HOUR_OF_DAY);

The example keeps the operation visible and gives you a starting point for using it in an application. When using year/month/day overload, the month is zero-based; leniency may normalize invalid dates.

Important Behavior and Edge Cases

• Core behavior: IntlCalendar represents a locale-aware ICU calendar. Month indexes are zero-based, while epoch time uses milliseconds.
• Return value: Check the result separately from changes to passed-in arrays, iterators, or object state.
• Data constraints: When using year/month/day overload, the month is zero-based; leniency may normalize invalid dates.
• Environment: The intl extension is required for this example.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• IntlCalendar::set helps you set one or more calendar fields.
• IntlCalendar represents a locale-aware ICU calendar. Month indexes are zero-based, while epoch time uses milliseconds.
• When using year/month/day overload, the month is zero-based; leniency may normalize invalid dates.
• DateTimeImmutable is often simpler for Gregorian dates; IntlCalendar is useful for ICU calendar systems.

IntlCalendar::set is useful when you need to set one or more calendar fields. Start with the small examples, then adapt the practical example while respecting its input and environment requirements.