Allow seconds in DateTime::from_str offset

src/datetime/tests.rs

@@ -793,6 +793,17 @@ fn test_datetime_from_str() {
             )
             .unwrap())
     );
+    assert_eq!(
+        "2015-2-18T13:16:9.15-10:00:00".parse::<DateTime<Utc>>(),
+        Ok(Utc
+            .from_local_datetime(
+                &NaiveDate::from_ymd_opt(2015, 2, 18)
+                    .unwrap()
+                    .and_hms_milli_opt(23, 16, 9, 150)
+                    .unwrap()
+            )
+            .unwrap())
+    );
     assert!("2015-2-18T23:16:9.15".parse::<DateTime<Utc>>().is_err());
 
     // no test for `DateTime<Local>`, we cannot verify that much.

src/format/parse.rs

@@ -578,6 +578,7 @@ where
 /// - `UTC` and `Z` are accepted as a valid timezone offset.
 /// - There can be a space between time and offset.
 /// - The colon in the offset may be missing.
+/// - The offset may optionally have seconds (compatible with the `Debug` format of `DateTime`).
 ///
 /// ```
 /// # use chrono::{DateTime, offset::FixedOffset};
@@ -604,7 +605,7 @@ impl str::FromStr for DateTime<FixedOffset> {
             Item::Fixed(Fixed::Nanosecond),
         ];
         const OFFSET_FORMAT: UtcOffsetFormat = UtcOffsetFormat {
-            precision: OffsetPrecision::Minutes,
+            precision: OffsetPrecision::OptionalSeconds,
             colons: Colon::Maybe,
             allow_zulu: true,
             padding: Pad::Zero,