tricky sentence

[evn108]

而吳黃龍已前雖引漢曆二十餘年，其實吳之首事。

 

I think I know what this sentence is saying, but I can't really figure out... how it is saying it? This is from an introduction to a history of the Southern Dynasties, in a section that is outlining the scope of the project and introducing the dynasties, how long each of them lasted, and the dating system (I believe it refers to the way dates are recorded within the text itself). So based on the context I think it means that the text will use Han reign names for the early history of Wu, even though at this point there are already Wu reign names. It follows a sentence that explains that this text begins in year one of the Xingping era of the Eastern Han (194), and ends in the final year of the Zhenming era of the Chen dynasty (589). But I can't figure out the grammar of the sentence? the 已前雖引 part is really tripping me up. The best I can come up with is "And (for events prior to) the end of the Huanglong era of Wu (229-231), although (I) cite the Han calendar for more than twenty years, this is the true beginning of the kingdom of Wu." Does that seem right? Or is there a better way to parse this?

[Publius]

已

19.同“以”。表示時間、方位、數量的界限。
 《孫子‧作戰》：“故車戰，得車十乘已上，賞其先得者。”
 《漢書‧文帝紀》：“年八十已上賜米人月一石，肉二十斤，酒五斗。”
 《儒林外史》第五回：“到了中秋已後，醫家都不下藥了。”

——《漢語大詞典》

[evn108]

Hmm so just "Before the Huanglong" then, rather than "before the end of the Huanglong?" I guess I should check if Huanglong year x etc. is ever actually used in the text.