Harvard Time: the seven-minute rule, and how Harvard sold the time

For generations, Harvard classes started seven minutes late on purpose. Long before that, Harvard's observatory was the clock that Boston and New England's railroads set their watches by, and it charged for the service.

Harvard Time: seven minutes late, on purpose

"Harvard Time" meant that a class listed for 10:00 actually began at 10:07. The seven minutes gave students and professors time to cross Harvard Yard between back-to-back classes, and everyone on campus knew to add them.

In April 2017 the Faculty of Arts and Sciences voted to end it. From fall 2018, most classes ran 75 minutes on a fixed grid with 15 minutes between them. The reason was geography: Harvard's School of Engineering and Applied Sciences was moving across the Charles River to a new campus in Allston, which opened in 2020, and students needed time to get between the two. Cambridge and Allston class times were staggered so that a student could finish in one and make it to the other.

When Harvard was New England's clock

In the mid-1800s every town kept its own local time, set by the sun. Boston, Worcester and Springfield were minutes apart, and trains ran on whatever the conductor's watch said. In 1853 a collision on a blind curve near Pawtucket, Rhode Island, caused by a conductor's faulty watch, killed 14 people.

The fix came from Harvard. In 1839 President Josiah Quincy invited the Boston clockmaker and astronomer William Cranch Bond to set up an observatory on campus, in a house where Lamont Library now stands. From 1849 the Harvard College Observatory kept the time for New England's railroads, at first by setting a chronometer and carrying it into Boston. In 1851 Bond began sending the time by telegraph, which the Harvard Gazette calls the world's first public time service. The observatory's electric "tick" reached Boston's fire-alarm system, which rang bells across the city at noon, and a time ball dropped each day so ships in Boston Harbor could set their chronometers.

By the 1870s, having Harvard time was a mark of status as well as accuracy. From 1872 the observatory charged for it, earning about $2,400 a year and around $3,000 in its last year, 1892, when the US Naval Observatory took over national time signals and companies like Western Union offered their own. Harvard Magazine tells the story through a regulator clock built in 1832 by Simon Willard Jr., wired to relay the observatory's time toward Boston.

The railroads' own solution came in 1883, when they adopted the four US time zones still used today. That story is in how railways created standard time.

Three Harvard discoveries about time

• Gravity changes the rate of time (1959–60). Robert Pound and Glen Rebka sent gamma rays 22.5 meters (74 feet) up and down a tower in Harvard's Jefferson Laboratory and measured the tiny frequency shift Einstein predicted, within about 10%. It was the first precise lab proof that clocks run at different rates at different heights. More in time dilation.
• The method behind atomic clocks. Harvard physicist Norman Ramsey developed the separated oscillatory fields method, which made atomic clocks far more precise, and with Daniel Kleppner built the hydrogen maser. He shared the 1989 Nobel Prize in Physics. See the history of atomic clocks.
• Your body clock runs about 24 hours and 11 minutes. In 1999, Charles Czeisler's team at Harvard Medical School and Brigham and Women's Hospital found that the human circadian clock averages about 24 hours 11 minutes, not the 25 hours earlier studies suggested, and is remarkably similar across ages. It's also why most people find it easier to stay up later than to go to bed earlier; see the jet lag calculator.

Other universities and time

Harvard wasn't alone. At Columbia, Isidor Rabi's molecular-beam magnetic resonance won the 1944 Nobel Prize and gave atomic clocks their founding idea. Observatories at Greenwich, Paris and Washington sold or broadcast time in much the same way Harvard did; Greenwich became the world's zero line in 1884 (see why the prime meridian is in Greenwich).

Sources

• The Harvard Crimson: "Harvard Time" to end (2017)
• Harvard Gazette: America's first time zone (2011)
• Harvard Magazine: How Harvard profited on keeping time (2021)
• The Harvard Crimson: When Harvard sold the time (2017)
• Pound–Rebka experiment
• Harvard Gazette: Human biological clock set back an hour (1999)

Questions people ask

What is Harvard Time?

The custom of starting Harvard classes seven minutes after the hour, so a 10:00 class began at 10:07, giving students time to walk between buildings. The Faculty of Arts and Sciences voted in April 2017 to end it, and from fall 2018 classes moved to a fixed schedule with 15 minutes between them.

Why did Harvard get rid of Harvard Time?

To make room for travel to the new engineering campus across the river in Allston, which opened in 2020. The new schedule staggers Cambridge and Allston start times and gives 15 minutes between most classes.

Did Harvard really sell the time?

Yes. From 1849 the Harvard College Observatory supplied accurate time to railroads and businesses, first by carrying a chronometer into Boston and from 1851 by telegraph. From 1872 it charged for the service, earning about $2,400 a year, until the US Naval Observatory took over in 1892.

What did Harvard prove about time and gravity?

In 1959–60 Robert Pound and Glen Rebka showed, in a 22.5-meter tower at Harvard's Jefferson Laboratory, that light climbing against gravity shifts in frequency by the tiny amount Einstein predicted. It was the first precise lab test that gravity changes the rate of time.