date-check: be more strict

ci/date-check/src/main.rs

@@ -41,13 +41,13 @@ fn make_date_regex() -> Regex {
         r"(?x) # insignificant whitespace mode
         (<!--\s*
           date-check:\s*
-          (?P<m1>\D+)\s+
+          (?P<m1>[[:alpha:]]+)\s+
           (?P<y1>\d{4})\s*-->
         )
         |
         (<!--\s*
           date-check\s*-->\s+
-          (?P<m2>\D+)\s+
+          (?P<m2>[[:alpha:]]+)\s+
           (?P<y2>\d{4})\b
         )
     ",