Many numbers are seen during the course of a day. Sometimes, a person remembers one or a few of what they've seen.

The most likely to be remembered when they're seen are numbers related to personal meaning, emotional significance, unusual construction, or otherwise seem remarkable. Why You Start Seeing Certain Numbers Again and Again talks about that.

Your birth time is likely to have personal meaning for you or be emotionally significant. It would be why you remember seeing 420 at least some of the times you notice it in your environment.

Wondering why a number is seen and remembered as often as it is, perhaps wondering if there's a special meaning or personal message associated with it, can give the number even more significance.

With the increased significance, and the fact that it's now a mystery the subconscious feels compelled to solve, will cause the person to remember seeing the number virtually every time it's seen. And, perhaps, actively scan the environment to locate every instance of the number — not all of which might have been noticed by casual attention. Why People See Certain Numbers All the Time addresses that.

The energy the number 420 represents includes family, home, and dependability.