The logic for investment is buying low and selling high and currently Bitcoin has a new ATHs is it safe to encourage new investor to buy now seeing how high the price has gone? My fear for new investors is that the don't experience a dip after buying since no one is sure of how far the new highs will reach.
It is not safe to buy if you are if you are going to play roulette.
If instead you are investing long-term in bitcoin because it is something you have studied, that you know its intrinsic properties, that you believe in its long-term future and its importance to human history, then the best day to buy bitcoin would be today. The second best day was yesterday, but you can't go back in time.