I don't know what's right, but what I do is mark the "trend".
So negative in the morning, postive in the afternoon = trending positive for the day
positive in the morning, positive in the afternoon, negative by evening = negative for the day.
Not sure if it's right, but it lets me know when the first day of positive is, and when the first day back to neg is.
As a disclaimer, I might suck at charting so....grain of salt.