Change timestamp parsing

src/verify.rs

@@ -287,7 +287,8 @@ fn parse_time(
     key: &'static str,
 ) -> Result<Option<DateTime<Utc>>, ParseSignatureError> {
     let r = hm.remove(key).map(|s| {
-        Utc.datetime_from_str(&s, "%s")
+        s.parse()
+            .map(|timestamp| Utc.timestamp(timestamp, 0))
             .map_err(|_| ParseSignatureError(key))
     });