It was after English inventor John Harrison (1693–1776) presented his ship’s chronometer to London’s Board of Longitude in 1736. The instrument was accurate to within one-tenth of a second per day (1.3 miles of longitude). Since it was set to the time of zero degrees longitude (Greenwich time), it enabled navigators to fix longitudinal position by determining local time. Even though Harrison’s award-winning invention was heavy (weighing 65 pounds), complicated, and delicate, it was subsequently improved upon so that it could be used on any sea-faring vessel in any weather conditions.