This hook pmpro_checkout_start_date allows you to change the start date of a membership before checkout. 

apply_filters( "pmpro_checkout_start_date", $startdate, int $user_id, object $pmpro_level );

Parameters

$startdate
$user_id
int;
$pmpro_level
object;

Source

File: https://github.com/strangerstudios/paid-memberships-pro/blob/master/preheaders/checkout.php

File: https://github.com/strangerstudios/paid-memberships-pro/blob/master/services/ipnhandler.php

File: https://github.com/strangerstudios/paid-memberships-pro/blob/master/services/twocheckout-ins.php

View in Source Code

About Actions and Filters in PMPro

Hooks allow you to extend Paid Memberships Pro without editing any core plugin files. You can use a hook to program custom code that interacts with or modifies code in our plugin, Add Ons, your theme, and even WordPress itself.

There are two kinds of hooks: actions and filters.

  • Action hooks allow you to run new custom code at pre-defined locations.
  • Filter hooks allow you change or extend existing code by modifying the data and returning it back to the software.

Click here to browse the full database of action and filter hooks available in Paid Memberships Pro. For help extending our Add Ons, refer to the individual Add On's documentation page for a list of available hooks.

For more developer-focused information about Paid Memberships Pro, check out the advanced developer topics documentation.