Today, with premium sakes that are being served chilled it is harder to mask stale or off-sake. As such there are several pointers that one can look for to make sure that you are getting sake that is fine for consumption. I like to tell customers that sake does well for about 14 months after bottling. Truthfully, sake keeps much longer and it becomes a factor of how adventurous you want to be. Many perceive "fresher is better" but I have had many sakes that were bottled a month or two before I tasted them and they tasted young, as if they had not fully grown up. Personally, I feel the flavor develops in the bottle in most cases, and as such it is not necessary to rush to the youngest bottling date. (Nama sakes are best consumed as fresh as possible!)
There is a movement in Japan to get bottling dates on more and more labels. Basically brewers didn't date bottles so that consumers wouldn't do what the gentleman mentioned above did. If you draw attention to the date then people will focus on it. There is no set place or type of date used in this process. Sometimes the date is on the main label, and sometimes it is on the back label. It is hard to see, as they use black typewritten letters usually in the traditional 04-07, which is 2004-July. We flip these number positions around in the US thus it would read 07-04. There is also another dating process, which uses the "Emperor's Calendar." This dating system begins each time a new emperor takes power. The last time this happened was 16 years ago in 1988. Thus the first year was 01 and this year of 2004 is 16. So if a label reads 16-03 then you can surmise that the sake was bottled in March of 2004. Likewise, if a date reads 15-02 then you would realize that this sake was bottled in February 2003. I would steer clear of sakes that were bottled in the year 14 as in 2002."
By the way January 2007 would read 19-01, so you basically want to steer clear of sakes with the year 17 on them. Also, if at all possible try to see the color of the sake! If it is yellow you may want to pass! If a bottle does not have a date, pick up four other sakes to see if they have dates. If those bottles have relatively fresh dates then assume that the bottle that you are looking at is legit! By all means take the bottle to the counter and ask the seller. If all else fails, ask what their return policy is, and make certain to return the brew if you get a mushroom-like nose and a flat feeling in a yellowish liquid. But please take heart in the fact that we are trying to really get all of our brewers to put dates on the bottles.