敬老の日 Keirou-no-hi means Respect for the Aged Day in Japan. It is another public holiday. It is held the third Monday of September every year.
Usually people will buy presents for the aging parents or grandparents, and department stores and grocery stores will have up special sections for popular gifts for the elderly. Some families may take the elders out to a special lunch or dinner. On the local news, many older people will be featured.
Overall, it is not a particularly important or historical holiday, but just a small way to show respect for the elderly and remember the efforts they put into raising us.