に至るまで【にいたるまで】

に至るまで means "all the way to", "right down to": a range reaches further than you would expect, and takes in even its far end. It follows a noun, very often in the frame AからBに至るまで, and it is formal and written.

B is the surprising end: the smallest detail, the most distant case. The sentence usually goes on to say that everything was covered, with すべて, はばひろく幅広く or だれ誰もが.

Up to the present

With a time, に至るまで runs a period up to a point, most often the present.

に至るまで or から～まで

から〜～まで states a range neutrally and fits any register. に至るまで adds weight: the range is wide or thorough. In conversation, plain まで does the job: 子供から大人まで.