By default, timezone in Opencart 3 is set to UTC. As a result, the incorrect operation of events related to time: for example, special offers.
It's so simpe to configure the correct timezone: open the file system/config/default.php and specify the desired time zone instead of UTC in the line:

// Date
$_['date_timezone']        = 'UTC';

For example, for Ukraine it will look like this:

// Date
$_['date_timezone']        = 'Europe/Kiev';

Here you can find the list of supported timezones: List of Timezones.

Don't forget to refresh caches after changes.