In the API it explains history(bar_count, frequency, field, ffill=True). I noted that "date/time" is not one of the available fields to use, but it would be quite useful especially when I want to use minute data. I am not sure whether it's safe to assume that there are 390 minutes in a trading day (6.5hr * 6); presumably not, as there may be days that trading did not last for the whole day.
My question is, how can I extend the history() function?