By default the store looks at the "date added" and not the "date created". The date added is a date assigned to a media on the day that media was added to the store.
You can change photostore to look at the date created if you would like. You must edit the tweak.php file of your photostore. The tweak.php is located in your store files at assets/includes/tweak.php.
Look for the setting:
$config['dateSearchField'] = 'date_added'; // Field to search when doing a date range search - date_added | date_created
// date_added = date added to library
// date_created = date file was created or photo was taken
Change the bolded part to 'date_created' and then save changes to that file on your hosting. Now your photostore will search the date created field.