lopers.google.com/protocol-buffers/docs/proto3#json">protobuf spec declares</a>:</p><table><thead><tr><th>Proto</th><th>JSON/YAML</th><th>Example</th><th>Notes</th></tr></thead><tbody><tr><td>Timestamp</td><td>string</td><td>“1972-01-01T10:00:20.021Z”</td><td>Uses RFC 3339, where generated output will always be Z-normalized and uses 0, 3, 6 or 9 fractional digits.</td></tr><tr><td>Duration</td><td>string</td><td>“1.000340012s”, “1s”</td><td>Generated output always contains 0, 3, 6, or 9 fraction