Standards There are several standards that specify date formats: ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times specifies YYYY-MM-DD (the separators are optional, but only hyphens are allowed to be used), where all values are fixed length numeric, but also allows YYYY-DDD, where DDD is the ordinal number of the day within the year, e.g. 2001–365. RFC 3339 Date and Time on the Internet: Timestamps specifies YYYY-MM-DD, i.e. a particular subset of the options allowed by ISO 8601. RFC 5322 Internet Message Format specifies day month year where day is one or two digits, month is a three letter month abbreviation, and year is four digits.
standards there are several standards that specify date formats iso 8601 data elements and interchange formats – information interchange – representation of dates and times specifies yyyy-mm-dd (the separators are optional but only hyphens are allowed to be used) where all values are fixed length numeric but also allows yyyy-ddd where ddd is the ordinal number of the day within the year eg 2001–365 rfc 3339 date and time on the internet timestamps specifies yyyy-mm-dd ie a particular subset of the options allowed by iso 8601 rfc 5322 internet message format specifies day month year where day is one or two digits month is a three letter month abbreviation and year is four digits