fix #2

I actually had this fixed locally for almost a month, but forgot to
commit and push it.
Thanks for reminding me @pepe!

1 files changed, 2 insertions, 1 deletions

diff --git a/date/init.janet b/date/init.janet
index 215b019..45d5209 100644
--- a/date/init.janet
+++ b/date/init.janet
@@ -41,10 +41,11 @@
        (map fun)
        from-pairs))
 
+(def- some? (complement nil?))
 (defn- put-date
   [ds key val]
   (assert (tm? ds))
-  (assert val)
+  (assert (some? val))
   (if (callable? val)
     (update ds key val)
     (put    ds key val)))