One of the most useful devices I've ever bought in my life is my Canon Wordtank IDF-3000, which is a little portable electronic Japanese dictionary. I got it for an absolute steal in Akihabara in 2001, for something like $100, and it's been so incredibly useful it's not even funny.
It has an English->Japanese dictionary, a Japanese->English dictionary, and more fun, a Japanese->Japanese dictionary, for some terms that just don't translate well (some previous Wordtanks simply didn't have those terms in the DB at all), as well as a kanji dictionary. In the straightforward E->J or J->E modes, they'll have sample sentences for the words as well as their meanings.
I'd been trying to figure out a way to tell exactly how outdated the sentences and colloquialisms were, and it finally came to me by accident the other day -- baseball!
Take, for example, a sample sentence for the word 試合, shiai, which means game or match or meeting, etc:
The Carp do not have a game today.
Okay, I'm with you so far. That sentence seems totally normal in 2006.
Now let's go with a sample sentence for the character 対, tai, which is used to denote a score or "vs." or whatnot:
The Hawks beat the Buffaloes 6-2.
(Lit: Daiei beat Kintetsu 6-2.)
Hmm. Well, that'd have been totally normal in 2001, so I can't fault them there either -- the Hawks were the Daiei Hawks and the Kintetsu Buffaloes still existed, so this is just funny to see, not wrong per se.
But let's go a little further. This one came from typing in the word 選手, senshu, which means baseball player:
Ochiai hit a home run.
Hiromitsu Ochiai, the current manager of the Chunichi Dragons, responsible for turning them into a force to be reckoned with, retired as a player in 1998 (at the age of 44! and a position player, at that!), but hasn't hit 20+ homers since 1996, and hasn't been a serious contender for an HR title since 1991. (stats here, stories here.) So that's putting these sample sentences into context of the early 1990's at best, although maybe this one was just using a random player for the sentence -- like we might use "Mark McGwire hit a home run" even though he's been retired for a couple of years. But here's the kicker:
The Whales won the game against the Carp.
(Lit: Taiyo beat Hiroshima.)
The Taiyo Whales became the Yokohama Bay Stars in the 1992-1993 offseason, so I think we've definitely got a dictionary sentence-writing date pegged now at somewhere around 1991 -- after the Hawks were sold to Daiei in 1988, at least, and before the Bay Stars changed their name.
Man, I'm a total dork.
But if you own a Japanese electronic dictionary, you should try a similar experiment; if nothing else, you might learn some new words!