Calligraphy generally does not write very detailed time, nor does it write Gregorian calendar and numbers. 20 12 is the Year of the Loong, which is an inauspicious year according to 60 years. And calligraphy can be signed with local governments, so your format can be:
Who (your name, usually only your first name without your last name, or your nickname) wrote a book in Beijing (or added the name of your study, such as Boyizhai), the place name and the name of the study can be added at the same time, for example ". . . . . . In Beijing Boyizhai ".
For example, Qiu Meng's Mo Shi Shu in the year of Renchen.
Qiu Meng Mohism was written in the year of Renchen.
Ren Chennian Qiu Meng Moshi Book Beijing Boyizhai