Index: dates.rkt
==================================================================
--- dates.rkt
+++ dates.rkt
@@ -19,15 +19,32 @@
 ;; Author contact information:
 ;;   joel@jdueck.net
 ;;   https://joeldueck.com
 ;; -------------------------------------------------------------------------
 
-;; Convenience functions for date strings
+;; Convenience functions for YYYY-MM-DD date strings
 
 (require gregor
          racket/string)
 
 (provide (all-defined-out))
 
-;; Ignores everything after the first space
+;; These functions ignore everything after the first space!
+(define (ymd->dateformat ymd-string dateformat)
+  (~t (iso8601->date (car (string-split ymd-string))) dateformat))
+
 (define (ymd->english ymd-string)
-  (~t (iso8601->date (car (string-split ymd-string))) "MMMM d, yyyy"))
+  (ymd->dateformat ymd-string "MMMM d, yyyy"))
+
+(module+ test
+  (require rackunit)
+  (check-equal? (ymd->english "2018-08-12") "August 12, 2018")
+  (check-equal? (ymd->dateformat "2018-08-12" "d MMM YYYY") "12 Aug 2018")
+
+  ;; How we handle weird input
+  (check-equal? (ymd->english "2018-08-12 everything after 1st space ignored") "August 12, 2018")
+  (check-equal? (ymd->english "2018-08 omitting the day") "August 1, 2018")
+  (check-equal? (ymd->english "2018 omitting month and day") "January 1, 2018")
+  (check-equal? (ymd->dateformat "2018-08-12") "123")
+
+  ;; Stuff we just don't handle
+  (check-exn exn:gregor:parse? (lambda () (ymd->english "2018-xyz"))))