Format of naming convention in English is under discussion at Wikipedia talk:Naming conventions (Chinese) and Wikipedia talk:Naming conventions (Chinese)/monarchical titles.
Emperor Wu of Jin China, sim. ch.晋武帝, trad. ch.晉武帝, py. jin4 wu3 di4, wg. Chin Wu-ti (between 234 and 236-May 17, 290) was a grandson of Sima Yi and the first emperor of the Jin Dynasty (265-420). Emperor Wu was known for his extravagance and sensuality, espcially after the unification of China after 280; legends boasted of his unimaginable potency over ten thousand concubines.
Han Wudi[?] was conventionally regarded as the first emperor to declare a nian hao; however he was only the first to use a nian hao in every year of his reign.
Han Wudi changed mottos every five years or so, going through a total of eleven slogans during his reign from 140 BC to 87 BC.
Thus 344 AD was the second year of Jianyuan of Jin Dynasty (or of Jin Kangdi) whereas 139 BC was the second year of Jianyuan of Han Dynasty (or of Han Wudi).