How to use the Xquery function fn:parse-ietf-date with a Google timestamp?

Question

It looks like this specific function chokes on the string which Google provides. For example:

Saturday, 2 December 2017 at 15:00:32 UTC

doesn't seem to parse, at least using the basex console with this function:

> 
> xquery fn:parse-ietf-date("Wed, 6 Jun 94 07:29:35 GMT") 
1994-06-06T07:29:35Z
Query executed in 0.82 ms.
> 
> xquery fn:parse-ietf-date("Sat, 2 December 2017 15:00:32 UTC") 
Stopped at ., 1/19:
[FORG0010] Invalid input ('-' expected, 'e' found): 'Sat, 2 December 2017 15:00:32 UTC'.
> xquery fn:parse-ietf-date("Sat, 2 Dec 2017 15:00:32 UTC") 
2017-12-02T15:00:32Z
Query executed in 3.45 ms.
> 
> xquery fn:parse-ietf-date("Sat, 2 Dec 2017 at 15:00:32 UTC") 
Stopped at ., 1/19:
[FORG0010] Invalid input (time expected, 'a' found): 'Sat, 2 Dec 2017 at 15:00:32 UTC'.
> 
> xquery fn:parse-ietf-date("Sat, 2 December 2017 15:00:32 UTC") 
Stopped at ., 1/19:
[FORG0010] Invalid input ('-' expected, 'e' found): 'Sat, 2 December 2017 15:00:32 UTC'.
> 

It looks like "at" causes havoc, as does a full month versus just an abbreviated month.

is this function able to parse this date? If not, what alternate function might be suitable?

Presumably Google's using a standard timestamp.

(data originates from "google hangouts" exported as JSON.)

Answer 1

When you look at the grammar of fn:parse-ietf-date() you notice not only the at but also the written out month is throwing the parser off; you could fix this using fn:replace() with a a regex like that:

parse-ietf-date(
  replace('Saturday, 2 December 2017 at 15:00:32 UTC', 
        '(\w+, \d+ [A-z]\w\w)\w+ (\d{4}) at',
        '$1 $2'
  )
)

Demo