After doing testing The publishing dates of our ads are not taking the timezone set in Joomla. To make ad display I had to set the 'Start Publishing' date to UTC time not based on the timezone set in Joomla.
Timezone: Australia/Darwin (UTC+10)
Test at 2017-09-20 10:00:00
Start Publishing (not working): 2017-09-20 09:59:00
Start Publishing (working): 2017-09-19 23:59:00
I tested this multiple time making sure any caching was not a issue. Buy looking at the database there is no timezone conversions happening.
Joomla make timezone conversion simple via the JDate class.