Source

File: wp-includes/class-wp-date-query.php

public function validate_date_values( $date_query = array() ) {
		if ( empty( $date_query ) ) {
			return false;
		}

		$valid = true;

		/*
		 * Validate 'before' and 'after' up front, then let the
		 * validation routine continue to be sure that all invalid
		 * values generate errors too.
		 */
		if ( array_key_exists( 'before', $date_query ) && is_array( $date_query['before'] ) ) {
			$valid = $this->validate_date_values( $date_query['before'] );
		}

		if ( array_key_exists( 'after', $date_query ) && is_array( $date_query['after'] ) ) {
			$valid = $this->validate_date_values( $date_query['after'] );
		}

		// Array containing all min-max checks.
		$min_max_checks = array();

		// Days per year.
		if ( array_key_exists( 'year', $date_query ) ) {
			/*
			 * If a year exists in the date query, we can use it to get the days.
			 * If multiple years are provided (as in a BETWEEN), use the first one.
			 */
			if ( is_array( $date_query['year'] ) ) {
				$_year = reset( $date_query['year'] );
			} else {
				$_year = $date_query['year'];
			}

			$max_days_of_year = gmdate( 'z', mktime( 0, 0, 0, 12, 31, $_year ) ) + 1;
		} else {
			// Otherwise we use the max of 366 (leap-year).
			$max_days_of_year = 366;
		}

		$min_max_checks['dayofyear'] = array(
			'min' => 1,
			'max' => $max_days_of_year,
		);

		// Days per week.
		$min_max_checks['dayofweek'] = array(
			'min' => 1,
			'max' => 7,
		);

		// Days per week.
		$min_max_checks['dayofweek_iso'] = array(
			'min' => 1,
			'max' => 7,
		);

		// Months per year.
		$min_max_checks['month'] = array(
			'min' => 1,
			'max' => 12,
		);

		// Weeks per year.
		if ( isset( $_year ) ) {
			/*
			 * If we have a specific year, use it to calculate number of weeks.
			 * Note: the number of weeks in a year is the date in which Dec 28 appears.
			 */
			$week_count = gmdate( 'W', mktime( 0, 0, 0, 12, 28, $_year ) );

		} else {
			// Otherwise set the week-count to a maximum of 53.
			$week_count = 53;
		}

		$min_max_checks['week'] = array(
			'min' => 1,
			'max' => $week_count,
		);

		// Days per month.
		$min_max_checks['day'] = array(
			'min' => 1,
			'max' => 31,
		);

		// Hours per day.
		$min_max_checks['hour'] = array(
			'min' => 0,
			'max' => 23,
		);

		// Minutes per hour.
		$min_max_checks['minute'] = array(
			'min' => 0,
			'max' => 59,
		);

		// Seconds per minute.
		$min_max_checks['second'] = array(
			'min' => 0,
			'max' => 59,
		);

		// Concatenate and throw a notice for each invalid value.
		foreach ( $min_max_checks as $key => $check ) {
			if ( ! array_key_exists( $key, $date_query ) ) {
				continue;
			}

			// Throw a notice for each failing value.
			foreach ( (array) $date_query[ $key ] as $_value ) {
				$is_between = $_value >= $check['min'] && $_value <= $check['max'];

				if ( ! is_numeric( $_value ) || ! $is_between ) {
					$error = sprintf(
						/* translators: Date query invalid date message. 1: Invalid value, 2: Type of value, 3: Minimum valid value, 4: Maximum valid value. */
						__( 'Invalid value %1$s for %2$s. Expected value should be between %3$s and %4$s.' ),
						'<code>' . esc_html( $_value ) . '</code>',
						'<code>' . esc_html( $key ) . '</code>',
						'<code>' . esc_html( $check['min'] ) . '</code>',
						'<code>' . esc_html( $check['max'] ) . '</code>'
					);

					_doing_it_wrong( __CLASS__, $error, '4.1.0' );

					$valid = false;
				}
			}
		}

		// If we already have invalid date messages, don't bother running through checkdate().
		if ( ! $valid ) {
			return $valid;
		}

		$day_month_year_error_msg = '';

		$day_exists   = array_key_exists( 'day', $date_query ) && is_numeric( $date_query['day'] );
		$month_exists = array_key_exists( 'month', $date_query ) && is_numeric( $date_query['month'] );
		$year_exists  = array_key_exists( 'year', $date_query ) && is_numeric( $date_query['year'] );

		if ( $day_exists && $month_exists && $year_exists ) {
			// 1. Checking day, month, year combination.
			if ( ! wp_checkdate( $date_query['month'], $date_query['day'], $date_query['year'], sprintf( '%s-%s-%s', $date_query['year'], $date_query['month'], $date_query['day'] ) ) ) {
				$day_month_year_error_msg = sprintf(
					/* translators: 1: Year, 2: Month, 3: Day of month. */
					__( 'The following values do not describe a valid date: year %1$s, month %2$s, day %3$s.' ),
					'<code>' . esc_html( $date_query['year'] ) . '</code>',
					'<code>' . esc_html( $date_query['month'] ) . '</code>',
					'<code>' . esc_html( $date_query['day'] ) . '</code>'
				);

				$valid = false;
			}
		} elseif ( $day_exists && $month_exists ) {
			/*
			 * 2. checking day, month combination
			 * We use 2012 because, as a leap year, it's the most permissive.
			 */
			if ( ! wp_checkdate( $date_query['month'], $date_query['day'], 2012, sprintf( '2012-%s-%s', $date_query['month'], $date_query['day'] ) ) ) {
				$day_month_year_error_msg = sprintf(
					/* translators: 1: Month, 2: Day of month. */
					__( 'The following values do not describe a valid date: month %1$s, day %2$s.' ),
					'<code>' . esc_html( $date_query['month'] ) . '</code>',
					'<code>' . esc_html( $date_query['day'] ) . '</code>'
				);

				$valid = false;
			}
		}

		if ( ! empty( $day_month_year_error_msg ) ) {
			_doing_it_wrong( __CLASS__, $day_month_year_error_msg, '4.1.0' );
		}

		return $valid;
	}