This is the customary date format defined in ISO 8601 and endorsed by the W3C.
这是 ISO 8601 定义并被 W3C 采纳的惯用日期格式。
Customary is used to describe something that a particular person usually does or has.
习惯上的 • Yvonne took her customary seat behind her desk. 伊冯娜坐在了她的书桌后面惯坐的位子上。