code: public static Timestamp ofTimeSecondsAndNanos(long seconds, int nanos) {
      checkArgument(
          Timestamps.isValid(seconds, nanos), "timestamp out of range: %s, %s", seconds, nanos);
      return new Timestamp(seconds, nanos);
    }
docs: Creates an instance representing the value of {@code seconds} and {@code nanos} since January
  1, 1970, 00:00:00 UTC.
  
  @param seconds seconds since January 1, 1970, 00:00:00 UTC. A negative value is the number of
  seconds before January 1, 1970, 00:00:00 UTC.
  @param nanos the fractional seconds component, in the range 0..999999999.
  @throws IllegalArgumentException if the timestamp is outside the representable range