大宋僧史略 1.19

1.19

又江表以今四月八日為佛生日者。依瑞應經也。如用周正。則合是今二月八日。今用建巳月。乃周之六月也。詳此。濫用建巳月者。有二意焉。一聞聲便用不摭實求時。一翻經者多用夏正。故斯謬耳。若如南山云。并眾生見聞不同。故時節不等。不宜確執。然則兩方相接。三藏所傳。以周昭時生。理為長也。

Furthermore, that Jiangbiao takes the current eighth day of the fourth month as the Buddha's birthday follows the Ruiying jing. If the Zhou calendar were used, it would properly be the current eighth day of the second month; using the month with the dipper pointing to si makes it the sixth month under the Zhou calendar. Examining this, there are two reasons for the mistaken use of the month with the dipper pointing to si: first, hearing the sound and immediately using it without verifying the reality to ascertain the season; second, translators of sūtras mostly used the Xia calendar, and thus this error occurred. If it is as Nanshan said, sentient beings differ in what they see and hear, so the seasons are not uniform, and one should not rigidly adhere [to one]. Nevertheless, where the two lands connect and what the Tripiṭaka has transmitted, taking him to have been born in the time of King Zhao of the Zhou has the most reasonable basis.