Custom field with advanced data selector showing the previous day

Hi,

This indicates a problem with the timezone. First, check that your website timezone (in the joomla configuration) is correct, that your PHP timezone is correct (in your php.ini) and that your joomla user timezone is also correct (in the settings of the user in the joomla user manager).
Finally, in the settings of the HikaShop date picker field plugin in the Joomla plugins manager, there is a setting to use noon instead of midnight when a day is selected. That way, even if there is a timezone issue, as long as it is less than 12 hours, it should still display the correct date.