Christmas GPS geohash
This is an achievement inspired by xkcd #201, "Christmas GPS". It is similar to the Origin and Displaced Origin geohashes in that it can be accomplished on any day. Within a graticule, take the birthday of yourself and your significant other, and put them after the decimal in the Lat and Long in any combination or format (mm-dd-yy, dd-mm-yyyy, etc) that provides a suitable place to meet.
Alternatively, since this doesn't really follow the geohash formula of the stock market opening price, etc. you could take the geohash coordinates on each of your birthdays, add them and take the mean value to find the hash point.
Cannot be combined with sex geohash, but bonus points if you go and make out like the comic suggests.