阿彌陀經疏 1.32

1.32

一時者，謂如是淨土之教，我聞當于某年某月某日也，而不言年等但云一時者，以諸國王制立時各不同故。如此土四時、彼三際；東夏以合朔為月旦、西乾以既望為月旦，兩方尚爾，四夷可知。既難以準定，故通言一時耳。

'At one time' means that this teaching of the Pure Land was heard by me on such-and-such a year, month, and day; yet it does not mention the year and so forth, but merely says 'at one time', because the royal calendars and temporal systems of various lands were each different. For example, this land has four seasons, while that land has three periods; the Eastern Xia (China) takes the conjunction of the sun and moon (new moon) as the first day of the month, while Western India takes the full moon as the first day of the month. If it is already like this between these two regions, what of the four barbarian lands? Since it is difficult to determine uniformly, it universally says 'at one time'.