Up to now refers to a period of time that has elapsed until the present moment. There are a variety of synonyms for this phrase, including "thus far," "hitherto," "as yet," and "until now." Each of these phrases can be used to convey the same meaning as up to now, but add a bit of a different nuance to the sentence. For example, "thus far" can be seen as a more formal way of expressing the same idea, while "as yet" implies that something is still pending. Regardless of which synonym one chooses to use, they all help the reader convey the intended message that something is true or has happened until the current point in time.