Revert "Merge pull request #13915 from edx/revert-13794-yro_implement-dateutil"

common/test/acceptance/tests/lms/test_lms_dashboard.py

lms/djangoapps/ccx/tests/test_field_override_performance.py

lms/djangoapps/courseware/context_processor.py

lms/djangoapps/courseware/date_summary.py

lms/djangoapps/courseware/tests/test_context_processor.py

lms/djangoapps/courseware/tests/test_course_info.py

lms/djangoapps/courseware/tests/test_credit_requirements.py

lms/djangoapps/courseware/tests/test_views.py

lms/djangoapps/courseware/views/index.py

lms/envs/common.py

lms/static/js/dateutil_factory.js

lms/static/js/spec/dateutil_factory_spec.js

...atic/js/student_account/views/account_settings_factory.js

lms/templates/course.html

lms/templates/courseware/accordion.html

lms/templates/courseware/course_about.html

lms/templates/courseware/progress.html

lms/templates/dashboard/_dashboard_course_listing.html

openedx/core/djangoapps/content/course_overviews/models.py

openedx/core/lib/tests/test_time_zone_utils.py