Regenerate C# and Objective-C.

csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs

@@ -41,17 +41,19 @@ namespace Google.Protobuf.WellKnownTypes {
   }
   #region Messages
   /// <summary>
-  /// A Timestamp represents a point in time independent of any time zone
-  /// or calendar, represented as seconds and fractions of seconds at
-  /// nanosecond resolution in UTC Epoch time. It is encoded using the
-  /// Proleptic Gregorian Calendar which extends the Gregorian calendar
-  /// backwards to year one. It is encoded assuming all minutes are 60
-  /// seconds long, i.e. leap seconds are "smeared" so that no leap second
-  /// table is needed for interpretation. Range is from
-  /// 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z.
-  /// By restricting to that range, we ensure that we can convert to
-  /// and from  RFC 3339 date strings.
-  /// See [https://www.ietf.org/rfc/rfc3339.txt](https://www.ietf.org/rfc/rfc3339.txt).
+  /// A Timestamp represents a point in time independent of any time zone or local
+  /// calendar, encoded as a count of seconds and fractions of seconds at
+  /// nanosecond resolution. The count is relative to an epoch at UTC midnight on
+  /// January 1, 1970, in the proleptic Gregorian calendar which extends the
+  /// Gregorian calendar backwards to year one.
+  ///
+  /// All minutes are 60 seconds long. Leap seconds are "smeared" so that no leap
+  /// second table is needed for interpretation, using a [24-hour linear
+  /// smear](https://developers.google.com/time/smear).
+  ///
+  /// The range is from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. By
+  /// restricting to that range, we ensure that we can convert to and from [RFC
+  /// 3339](https://www.ietf.org/rfc/rfc3339.txt) date strings.
   ///
   /// # Examples
   ///

objectivec/google/protobuf/Timestamp.pbobjc.h

@@ -56,17 +56,19 @@ typedef GPB_ENUM(GPBTimestamp_FieldNumber) {
 };
 
 /**
- * A Timestamp represents a point in time independent of any time zone
- * or calendar, represented as seconds and fractions of seconds at
- * nanosecond resolution in UTC Epoch time. It is encoded using the
- * Proleptic Gregorian Calendar which extends the Gregorian calendar
- * backwards to year one. It is encoded assuming all minutes are 60
- * seconds long, i.e. leap seconds are "smeared" so that no leap second
- * table is needed for interpretation. Range is from
- * 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z.
- * By restricting to that range, we ensure that we can convert to
- * and from  RFC 3339 date strings.
- * See [https://www.ietf.org/rfc/rfc3339.txt](https://www.ietf.org/rfc/rfc3339.txt).
+ * A Timestamp represents a point in time independent of any time zone or local
+ * calendar, encoded as a count of seconds and fractions of seconds at
+ * nanosecond resolution. The count is relative to an epoch at UTC midnight on
+ * January 1, 1970, in the proleptic Gregorian calendar which extends the
+ * Gregorian calendar backwards to year one.
+ *
+ * All minutes are 60 seconds long. Leap seconds are "smeared" so that no leap
+ * second table is needed for interpretation, using a [24-hour linear
+ * smear](https://developers.google.com/time/smear).
+ *
+ * The range is from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. By
+ * restricting to that range, we ensure that we can convert to and from [RFC
+ * 3339](https://www.ietf.org/rfc/rfc3339.txt) date strings.
  *
  * # Examples
  *