Wikipedia gives the date for Chinese mathematician Zhu Shijie's Jade Mirror of the Four Unknowns (四元玉鉴, Siyuan yujian) as 1303, citing
Elman, Benjamin A. (2005). On their own terms science in China, 1550-1900. Cambridge, Mass.: Harvard University Press. p. 252. ISBN 0674036476.
That reference says
On the other hand, the editors had not yet recovered Zhu Shijie's Jade Mirror of the Four Unknowns (Siyuan yujian) and his 1299 Primer of Mathematics in time for inclusion in the Qianlong Imperial Library.
Searching Google Books and Amazon Look Inside I do not find any other references in this work to the year 1303.
I'd like to know where this information comes from to be so casually dropped into the text. Usually dates like these are hard-won pieces of information, stitched together from different calendars or more obscure references, and scholars generally leave information on how they determine these things. I would expect a date to be expressed something like Dàdé 7 (the seventh year in the second era of Temür Khan's reign; note I'm neither a historian nor familiar with Chinese dates).