fix error str for weekdays

src/datetime.rs

@@ -87,7 +87,7 @@ impl FromStr for Weekdays {
         if has_valid || !has_invalid {
             Ok(Weekdays { bits })
         } else {
-            Err(anyhow!("invalid time, must be hh:mm"))
+            Err(anyhow!("invalid weekdays (expected like \"Mon,Tue,Wed\")"))
         }
     }
 }