How Romans kept time

[guy]

It’s been a while since there was a post on how Ancient Romans kept time (see below)

Ancient Romans measured time with flexible "seasonal hours" rather than fixed 60-minute increments, relying primarily on sundials, water clocks, and public sky-watchers.

The fundamental difference in Roman timekeeping was that an hour was not a fixed duration.

12 Daytime Hours: The period between sunrise and sunset was divided into 12 equal hours (horae). As a result, a summer daytime hour could last up to 75 modern minutes, while a winter daytime hour could shrink to around 45 modern minutes.

 

Four Nighttime Watches: The night was divided into four military watches (vigiliae), each monitored by night watchmen and soldiers on duty.

The system became so familiar that Romans used the watches as standard time references. Instead of saying "about 2:00 a.m.," someone might describe an event as occurring during the third or fourth watch. Literary sources, military accounts, and later Christian texts often use these expressions because they were immediately understood by contemporary audiences.

The Romans didn’t usually divide the night into watches as we do. In military settings, they often relied on water clocks (clepsydrae) and designated officers to mark the watches. Historical sources describe how water clocks measured portions of the night and signaled when it was time to change watches. As water flowed from one vessel to another, it helped keep each interval reasonably consistent.

 

 Water Clocks (Clepsydrae): Because sundials were useless at night or on cloudy days, Romans relied on water clocks (clepsydrae), which measured time by the regulated flow of water from one vessel into another.

 

Civic Timekeeping: The Accensus:

Before sundials were widespread in Rome, time was announced publicly by civic officials:

1. An official assistant called an accensus stood on the steps of the Senate house (Curia).

2. When the sun crossed the meridian between the Rostra [the main speaker's platform in the Roman Forum] and the Graecostasis [nearby platform where foreign ambassadors and visitors waited], the accensus shouted: "Noon!" (Meridies) across the forum.

3. Another shout marked the late afternoon (suprema), signaling the official end of judicial business.

The Roman meridies ("midday") was fundamentally an astronomical event: the moment the sun crossed the local meridian and reached its highest point in the sky. That event itself did not drift with the seasons. Every day has a meridies, whether it is summer or winter.

So if you had stood in the Forum:

• On a summer day, meridies would still be the midpoint between sunrise and sunset, but it would arrive after a longer sequence of daylight hours.
• On a winter day, meridies would still be the midpoint of the shorter daylight period.
• The announcement itself was triggered by the sun's position, not by a fixed numerical hour on a clock.

In other words, the length of the Roman hours varied with the seasons, but meridies itself was always the moment the sun crossed the meridian. The Romans treated noon as a natural event, not a fixed number on a clock.

The largest deviations of the meridies occur approximately:

• Around 11 February: about 14 minutes early.
• Around 3 November: about 16 minutes late.

So if you could somehow place an accurate modern clock in the Roman Forum, the accensus might call"Meridies!" at something equivalent to approximately 11:46 a.m. on one part of the year and 12:16 p.m. on another. But no Roman would have noticed or cared, because noon was defined by the Sun's position, not by a numbered clock face.

 

 

Below are several short videos on the subject, along with one long video:

 

 

 

 

 

 

 

 

Edited 48 minutes ago by guy