Yes, you can omit に in that case. You only need it for concrete times and dates, not nouns like "tomorrow", or "last week".
I'm assuming that you are relatively new to Japanese as well? Did you write the other comment too?
I'd be careful about starting to omit things at such an early stage of learning, because you need to learn the grammatical rules first. The first goal is to learn proper Japanese, not speak like a native. They'll be plenty of that later on. In my experience, I would be careful about taking grammatical advice from my Japanese friends unless they actually do know what they are talking about (as in know the grammar rules, which most natives of any language don't). I've gotten just plain grammaticaly wrong advice from friends before, and learned bad habits and highly substandard language (according to my teacher). Practice with your friends, of course, but just make sure you're learning the right material.
Yes, you can omit に in that
Yes, you can omit に in that case. You only need it for concrete times and dates, not nouns like "tomorrow", or "last week".
I'm assuming that you are relatively new to Japanese as well? Did you write the other comment too?
I'd be careful about starting to omit things at such an early stage of learning, because you need to learn the grammatical rules first. The first goal is to learn proper Japanese, not speak like a native. They'll be plenty of that later on. In my experience, I would be careful about taking grammatical advice from my Japanese friends unless they actually do know what they are talking about (as in know the grammar rules, which most natives of any language don't). I've gotten just plain grammaticaly wrong advice from friends before, and learned bad habits and highly substandard language (according to my teacher). Practice with your friends, of course, but just make sure you're learning the right material.