When the membership contribution process is executed, all the memberships assigned have a transaction date that equals the Process Date. It should be the same as the qualifying revenue date, because we are "granting" the membership based on the date that we received the gift, not based on the date we ran the process. 

Perhaps this could be a configuration option - so different customers can choose whether the membership transaction that is added by the process has a date that matches the process date or the revenue transaction date. For organizations who do not run MCP on a daily basis, or if the process completes after midnight, the dates never match and there is no alternate way to set this date in an automated manner.