Raise proper exception when month argument is not a name

https://bugs.ruby-lang.org/issues/17485#change-89871
(cherry picked from commit 0867b638aff9ec192ca420a44ffa5a77c892e8f2)

1 files changed, 3 insertions, 9 deletions

diff --git a/time.c b/time.c
index 8f044e1e59..77f42fc89a 100644
--- a/time.c
+++ b/time.c
@@ -2789,9 +2789,10 @@ month_arg(VALUE arg)
         return obj2ubits(arg, 4);
     }
 
+    mon = 0;
     VALUE s = rb_check_string_type(arg);
     if (!NIL_P(s) && RSTRING_LEN(s) > 0) {
-        mon = 0;
+        arg = s;
         for (i=0; i<12; i++) {
             if (RSTRING_LEN(s) == 3 &&
                 STRNCASECMP(months[i], RSTRING_PTR(s), 3) == 0) {
@@ -2799,15 +2800,8 @@ month_arg(VALUE arg)
                 break;
             }
         }
-        if (mon == 0) {
-            char c = RSTRING_PTR(s)[0];
-
-            if ('0' <= c && c <= '9') {
-                mon = obj2ubits(s, 4);
-            }
-        }
     }
-    else {
+    if (mon == 0) {
         mon = obj2ubits(arg, 4);
     }
     return mon;