Japanese people are known to be punctual. Even their trains arrive at the exact time it said it would and when meeting up with someone else, people tend to show up fifteen minutes before the agreed time.
Minutes, even seconds, matters to Japanese. They value time so much that whenever they are late, they tend to deeply apologize to their colleagues. For trains, even if it arrives a minute late, they immediately announce their apologies through the speakers. Major railway systems also hand out a certificate of lateness that you may show to your employer or teacher as a proof why you were late. Most Japanese citizens have already computed the time they need to get to their destination thus resulting to the choice of time for the train departure. The annual average delay of the Shinkansen is only 0.9 minutes so you surely won't be late for your appointment once you board it.
Many children are raised to be time conscious that when they go to other countries, they are often shocked that tardiness is somehow accepted.
As the saying goes, when in Japan, do what the Japanese do. As soon as you arrive in Japan, make sure your watch is in sync with the Japan Standard Time!