How do you format date-times in RFC 3339 style?

[sirgazil]

Hi,

I'm generating atom feeds from SXML that don't validate because of the 
date-time format I'm using:

> (use-modules (srfi srfi-19))
> (date->string (current-date) "~Y-~m-~dT~H:~M.~S~z")
$1 = "2019-02-11T13:42.57-0500"

String $1 is close to the RFC 3339 style,¹ which is the required format 
for atom feeds, but the time zone offset should be -05:00, and Guile's 
SRFI-19 ~z time zone escape is RFC 822 style, which formats the time 
zone offset as -0500.

What should I do to get the offset in the required format?


Thanks,


_____

1. http://www.faqs.org/rfcs/rfc3339.html


--
Luis Felipe López Acevedo
http://sirgazil.bitbucket.io/