Fix behavior of datetime formatting (#3790)

rust-runtime/aws-smithy-types/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aws-smithy-types"
-version = "1.2.1"
+version = "1.2.2"
 authors = [
     "AWS Rust SDK Team <aws-sdk-rust@amazon.com>",
     "Russell Cohen <rcoh@amazon.com>",

rust-runtime/aws-smithy-types/src/date_time/mod.rs

@@ -332,7 +332,12 @@ impl Ord for DateTime {
 
 impl Display for DateTime {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let date = self.fmt(Format::DateTime).map_err(|_| fmt::Error)?;
+        // Some dates are out of range to be serialized with `DateTime`.
+        // In these cases, fallback to using epoch seconds which always works
+        let date = match self.fmt(Format::DateTime) {
+            Ok(date) => date,
+            Err(_err) => format::epoch_seconds::format(self),
+        };
         write!(f, "{}", date)
     }
 }
@@ -629,6 +634,13 @@ mod test {
         );
     }
 
+    #[test]
+    fn formatting_of_early_dates() {
+        let date: DateTime =
+            DateTime::from_str("Mon, 16 Dec -019 23:48:18 GMT", Format::HttpDate).unwrap();
+        assert_eq!(format!("{}", date), "-62736509502");
+    }
+
     #[test]
     fn ord() {
         let first = DateTime::from_secs_and_nanos(-1, 0);