Milestones of the Hong Kong Observatory Time Service

Local time was determined by astronomical observations at the Observatory by using a 6-inch Lee Equatorial and a 3-inch Transit Circle.

Time signals were indicated by dropping a time ball at 13:00 hour each day.

Greenwich Mean Time (GMT) was adopted as Hong Kong Official Time.

The Leroy 1350 Pendulum Clock was installed in 1924. It is the oldest surviving instrument in support of the Observatory’s time service.

Pendulum clock was installed and regulated by radio time signals from other centres. Timing accuracy gradually improved from seconds to within one-fifth of a second.

Quartz controlled timing system was used to replace the pendulum clock. Accuracy was increased to 80 milliseconds. HKO also directly broadcast the 6-pip time signal on 95 MHz until 1989.

Coordinated Universal Time (UTC) was adopted as Hong Kong official time standard.

The first Caesium Beam Atomic Clock was acquired with an accuracy to fractions of a microsecond per day.

Telephone Information Enquiry system was put into operation to provide time check through telephone.

Network time service was lanuched. Members of the public can synchronize their computer clock with the Hong Kong Observatory's time servers.

Hong Kong Observatory used a high accuracy Time Transfer System to provide time information of it's atomic clock to the Bureau International des Poids Measures (BIPM) for UTC determination.