Discount a Paid Memberships Pro level half way through the year.

pmpro_checkout_level.php

<?php
/*
 * Add this code into a custom plugin. Combine this with the pmpro-set-expiration-date and/or pmpro-subscription-delay plugins
 * to have memberships expire/renew on the same date, e.g. Y2-01-01 to expire/renew on Jan 1 next year.
 *
 * You can update the logic to check for different months or adjust the price in a different way. The code below divides the
 * initial payment by 2 July 1 through Dec 31.
 */
function pmpro_checkout_level_half_off_mid_year( $level ) {
	$month = date( 'n', current_time( 'timestamp' ) );
	if ( $month > 6 ) {
		//July or later
		if ( $level->initial_payment > 0 ) {
			$level->initial_payment = number_format( $level->initial_payment/2, 2 );
		}
	}

	return $level;
}
add_filter( 'pmpro_checkout_level', 'pmpro_checkout_level_half_off_mid_year' );