Use international date format (ISO)

W3C 中 W3C QA - Quality Tips for Webmasters ，裡面有篇資料 Use international date format (ISO) 轉述給各位參考：

The international format defined by ISO (IS0 8601) tries to address all these problems by defining a numerical date system as follows: YYYY-MM-DD where * YYYY is the year [all the digits, i.e. 2012]
* MM is the month [01 (January) to 12 (December)]
* DD is the day [01 to 31]

For example, "3rd of April 2002", in this international format is written: 2002-04-03.