Because our trading market is divided into morning and night, there is no way to set a different transaction time in the same database and the same commodity.
@junjun, I don't really see a question.
You might want to do a SEARCH on "time" and see if any of the already existing threads can help you.
And after that, you could be more specific with your question, or issue.
Could you please check Amibroker's File > Database Settings > Intraday Settings window?