The Great Mosque of Solo in Central Java features an Istiwa clock, sometimes called a Jam. This clock is a legacy of Pakubuwono VIII, dating from 1784 in Java or 1855 AD.
The function of this clock is to determine prayer times. This Istiwa clock works by using parallel shadows cast by sunlight. Istiwa clocks have hands aligned north-south.
In 1784, there were no clocks in Java like those we have today. On the advice of palace scholars, PB VIII made a special clock. Because it uses sunlight, this clock can practically only be used to mark the times of Zuhr and Asar prayers.