STEPS TO REPRODUCE

1. Change site's Timezone configuration (eg UTC 0)
2. Create a course setting a start date
   1. Check the Unix timestamp at mdl_course.startdate, it's created base on the current timezone configuration
3. Modify the site's Timezone configuration (eg UTC -5)
   1. Check that mdl_course.start hasn't changed
4. Course settings and topics shows now a different starting date (eg a day earlier)
   1. Weekly topics are released with hours of difference (eg 3AM instead 8AM)

EXPECTED

Weekly format will work with the configured timezone, releasing the course and topics in the configured date (and time) on course settings.

RESULT

Course start date and weekly topics are released in different date/time initially configured.