the end of december and the beginning of january are the busiest times for the japanese post offices. the japanese have a custom of sending New Year's Day postcards (年賀状, nengajō) to their friends and relatives. it is similar to the western custom of sending christmas cards. their original purpose was to give your faraway friends and relatives tidings of yourself and your immediate family. in a manner of speaking, this custom existed for people to tell others whom they did not often meet that they were alive and well.
japanese people send these postcards so that they arrive on the 1st of january. the post office guarantees to deliver the greeting postcards by the first of january if they are posted within a time limit, from mid-december to near the end of the month and are marked with the word nengajo. in order to deliver these cards on time, the post office usually hires students part-time to help deliver the letters.
it was fun during my years in japan to receive a nengajo from friends. 2009 is the year of the ox so there are a lot of ox shown on nengajos.