Symptoms
After upgrade to London, Customer found an issue with field 'planned end date' present on project task form which shows the incorrect value {"status":"success","date":} for new project task as well on existing project task
Release
London-patch3
Cause
Custom Script include 'AjaxProjectTaskUtil'
Resolution
Reverting back the script include to OOTB resolves the issue
Additional Information
Script include "AjaxProjectTaskUtil" is responsible to calculate the end date and duration for the projects and project tasks which is being called by client script "Calculate End Date From Duration". This script include should be OOTB to avoid this kind of issues.