"How is your day been" is grammatically incorrect in English. It is impossible to say "X is been." The auxiliary verb required for "been" is "has." The question, then, is "how has your day been" (often contracted to "how's your day been, where "'s" = "has"). Now, the difference between "how has your day been" and "how is your day" is a question of emphasis on the time. "How has your day been" is asking you how your entire day has been up until now. "How is your day" does not emphasize this "entire duration of the day." It *could* be interpreted as "how is your day at this moment." The same difference applies to "today *has* been a busy day" and "today is a busy day." The former really emphasizes the entire duration of the day, until this very point, from the very beginning of the day. The latter makes no such emphasis.