fix: truncate milliseconds to i64 before serializing

time/src/serde/timestamp/milliseconds.rs

@@ -17,14 +17,15 @@ pub fn serialize<S: Serializer>(
     datetime: &OffsetDateTime,
     serializer: S,
 ) -> Result<S::Ok, S::Error> {
-    let timestamp = datetime.unix_timestamp_nanos() / 1_000_000;
+    // Truncating should be fine until year 2262
+    let timestamp = (datetime.unix_timestamp_nanos() / 1_000_000) as i64;
     timestamp.serialize(serializer)
 }
 
 /// Deserialize an `OffsetDateTime` from its Unix timestamp with milliseconds
 pub fn deserialize<'a, D: Deserializer<'a>>(deserializer: D) -> Result<OffsetDateTime, D::Error> {
-    let value: i128 = <_>::deserialize(deserializer)?;
-    OffsetDateTime::from_unix_timestamp_nanos(value * 1_000_000)
+    let value: i64 = <_>::deserialize(deserializer)?;
+    OffsetDateTime::from_unix_timestamp_nanos((value as i128) * 1_000_000)
         .map_err(|err| de::Error::invalid_value(de::Unexpected::Signed(err.value), &err))
 }