Student or Learner
I have got a question , what does "I don't know up to now" mean?
Which one is correct "I don't know up to now" or "I didn't know up to now"?
"I don't know up to now" is not natural. It would mean that you do not know and you continue to not know. So, simply "I don't know" would suffice.
"I didn't know up to now" is a little better. It means that you just learned. You know now, but you did not until this very moment.
"I didn't know until now" is the natural way to say this.