XPath/XQuery parse-ietf-date function

Parses a string containing the date and time in IETF format, returning the corresponding xs:dateTime value.

The function accepts a string matching the production input in the following grammar:

The input is case-insensitive: upper-case and lower-case distinctions in the above grammar show the conventional usage, but otherwise have no significance.

If the input is an empty sequence, the result is an empty sequence.

The dayname, if present, is ignored.

The daynum, monthname, and year supply the day, month, and year of the resulting xs:dateTime value. A two-digit year must have 1900 added to it. A year such as 0070 is to be treated as given; negative years are not permitted.

The hours, minutes, and seconds (including fractional seconds) values supply the corresponding components of the resulting xs:dateTime value; if the seconds value or the fractional seconds value is absent then zero is assumed.

If both a tzoffset and a tzname are supplied then the tzname is ignored.

If a tzoffset is supplied then this defines the hours and minutes parts of the timezone offset:

• If it contains a colon, this separates the hours part from the minutes part.

• Otherwise, the grammar allows a sequence of from one to four digits. These are interpreted as H, HH, HMM, or HHMM respectively, where H or HH is the hours part, and MM (if present) is the minutes part.

• If the minutes part is absent it defaults to 00.

If a tzname is supplied with no tzoffset then it is translated to a timezone offset as follows:

If neither a tzoffset nor tzname is supplied, a timezone offset of 00:00 is assumed.