dates: conform RFC-3339 standard

1 files changed, 21 insertions, 1 deletions

diff --git a/src/dates.scm b/src/dates.scm
index e9c9b0c..a70aa01 100644
--- a/src/dates.scm
+++ b/src/dates.scm
@@ -1,4 +1,5 @@
 (define-module (src dates)
+  #:use-module (ice-9 format)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-19)
   #:export (string/ISO->date
@@ -12,7 +13,26 @@
   (string->date string "~Y-~m-~d"))
 
 (define (date->string/RFC3339 date)
-  (date->string date "~4"))
+  (call-with-output-string
+    (lambda (p)
+      (let* ((offset           (abs (date-zone-offset date)))
+             (rem-h-seconds    (modulo offset (* 60 60)))
+             (offset-hours     (floor (/ (- offset rem-h-seconds) 60 60)))
+             (rem-m-seconds    (modulo rem-h-seconds 60))
+             (offset-minutes   (floor (/ (- rem-h-seconds rem-m-seconds) 60))))
+       (format
+         p
+         "~4,'0d-~2,'0d-~2,'0dT~2,'0d:~2,'0d:~2,'0d~:[Z~;~c~2,'0d:~2,'0d~]"
+         (date-year date)
+         (date-month date)
+         (date-day date)
+         (date-hour date)
+         (date-minute date)
+         (date-second date)
+         (not (= 0 (date-zone-offset date)))
+         (if (< 0 (date-zone-offset date)) #\+ #\-)
+         offset-hours
+         offset-minutes)))))
 
 (define unix-date (string/ISO->date "1970-01-01"))