PHP cal_to_jd() Function: Usage and Examples

Converts a date in a supported calendar into a Julian day number.

What Is cal_to_jd() in PHP?

Converts a date in a supported calendar into a Julian day number.

Its syntax is:

cal_to_jd(int $calendar, int $month, int $day, int $year): int

Parameters:

• $calendar — Accepted as int; required argument.
• $month — Accepted as int; required argument.
• $day — Accepted as int; required argument.
• $year — Accepted as int; required argument.

Return type: int. Validate input dates separately; day-number conversion should not be used as a replacement for validation.

Availability: Requires the calendar extension.

Example 1: Basic Usage

<?php

echo cal_to_jd(CAL_GREGORIAN, 1, 1, 2025);

Output:

2460677

Validate input dates separately; day-number conversion should not be used as a replacement for validation.

Example 2: A Different Input

<?php

echo cal_to_jd(CAL_GREGORIAN, 12, 31, 2025);

Output:

2461041

Validate input dates separately; day-number conversion should not be used as a replacement for validation.

Practical Example: Applying It in a Program

<?php

$firstDay = cal_to_jd(CAL_GREGORIAN, 1, 1, 2025); $lastDay = cal_to_jd(CAL_GREGORIAN, 1, 31, 2025); echo $lastDay - $firstDay;

Output:

30

Validate input dates separately; day-number conversion should not be used as a replacement for validation.

Important Behavior and Edge Cases

• Key behavior: Validate input dates separately; day-number conversion should not be used as a replacement for validation.
• Environment: Requires the calendar extension.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Converts a date in a supported calendar into a Julian day number.
• Validate input dates separately; day-number conversion should not be used as a replacement for validation.
• Requires the calendar extension.

Summary: Validate input dates separately; day-number conversion should not be used as a replacement for validation.