With the introduction of Railway Time , time zones and Standard Time became the norm.
Local time is calculated by the line of longitude at which a town is placed.
So Oxford Time is 5 minutes and 2 seconds behind Greenwich Time. This dates from the foundation of the college when the bell rang once for each of the college's original 101 students, in order to tell them to return to the college before the gates were locked. The Tom Tower at Christ Church, Oxford was built by Sir Christopher Wren . Christ Church was founded in 1524 by Cardinal Wolsey as Cardinal College and refounded as Christ Church by Henry VIII in 1546 on his fall from grace. Tom Tower, above the main gate, was designed by Sir Christopher Wren in 1681 and houses the bell Great Tom.