getDaysInMonth()

Returns the number of days in a given month of a specific year. Correctly handles leap years when calculating February.

Syntax

getDaysInMonth(date)
getDaysInMonth(year, month)

Parameters

Parameter	Type	Required	Description
date	Date	Yes (overload 1)	The date object whose month to examine
year	number	Yes (overload 2)	The Gregorian year (1–9999)
month	number	Yes (overload 2)	The month (1–12)

Returns

number - The number of days in the specified month

Basic Examples

Using a Date Object

import { getDaysInMonth } from 'date-and-time';

getDaysInMonth(new Date(2024, 1, 1)); // => 29 (Feb 2024, leap year)
getDaysInMonth(new Date(2023, 1, 1)); // => 28 (Feb 2023, not a leap year)
getDaysInMonth(new Date(2025, 0, 1)); // => 31 (January 2025)

Using Year and Month Numbers

import { getDaysInMonth } from 'date-and-time';

getDaysInMonth(2024, 2); // => 29 (Feb 2024, leap year)
getDaysInMonth(2023, 2); // => 28 (Feb 2023, not a leap year)
getDaysInMonth(2025, 4); // => 30 (April 2025)
getDaysInMonth(2025, 12); // => 31 (December 2025)

See Also

• isLeapYear() - Check if a year is a leap year
• addMonths() - Add months to a date