Sorry if this is off topic, but today is respect for the aged day in Japan, and I'm unsure how to greet elderly individuals, if at all. What would be the proper greeting? Would one greet individuals they pass on the street?
I don't consider myself an authoritative source, but I did a little searching and found this link that has a bunch of phrases to say on respect for the aged day (敬老の日):
Honestly, I would feel awkward saying many of these myself and might just use a safe "こんにちは” (with a smile), but maybe you could try something like this (from the above list):
There are indeed a bunch of phrases to say for respect for the aged day in the site introduced by Locksleyu. But as you know the elderly of Japan, I mean people over the age of 70, are healthy, therefor I think you are better not to use the expression like "いつまでも長生きしてください Please stay healthy forever", instead you should say "いつもお元気ですね You always look healthy" or "いつもお若いですね lit. You always look young, aren't you?"
To tell you the truth, in the phrase "これからも、元気でずっと長生きしてくだい" or "いつまでも長生きしてください" in Japanese, there is a nuance that the person seems to be unable to live long enough. This kind of greeting may be permitted if it is given to a bedridden old person, but it is not suitable for the elderly who can respond cheerfully to your visit, or for those, even if they are over 70 years old, who are spending their leisure time by enjoying sports, traveling, hobbies and the like.