I can't seem to find anywhere how to make a Roman sundial so I'm wondering if anyone can tell me how or where I can find how to make a Roman sundial?

I'm also wondering how Roman time works and how it is kept?

  • 2
    Three comments: (1) You have a previous unregistered account with the same name. Should we merge that old account to this new one? (2) The question is interesting, but the connection to Latin language is not clear. It also contains two different questions. Could you formulate it into a single question, related to the language? Perhaps something like "How did Romans describe sundial readings in Latin?" – the formulation is up to you. Separate questions should be asked separately. (3) Welcome to the site!
    – Joonas Ilmavirta
    Commented Sep 15, 2016 at 4:51
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    I think you might get a better answer on the "History of science and mathematics" site. It is a somewhat complicated business (seasonal hours vs equinoctial hours...)
    – fdb
    Commented Sep 15, 2016 at 8:09
  • The clepsydra, originating in Egypt or Athens, measured time from the falling water-level in a jug with a controlled leak. Alfred the Great measured time from marks on a candle. However Cicero does have a word for sun-dial 'solarium', and Censor, 'horarium.'
    – Hugh
    Commented Sep 17, 2016 at 23:35

1 Answer 1


One of the best primary sources for sundials is from Vitruvius, "On Architecture", book 9. He describes mathematically how to construct a sundial based on the works of the earlier Greek philosophers.

One hōra (hour) was always 1/12 of the time from sunrise to sunset, regardless of how long the day was. This made timekeeping without a sundial significantly easier (since the sun is always in roughly the same place for any given hour), and made constructing a sundial easier as well. Vitruvius's construction is a bit difficult to follow in text, but doesn't require particularly complicated mathematics, and—most importantly—doesn't require much adjustment once the sundial is finished.

As far as how Romans actually kept time, that depends on the period you're talking about. In general the day was divided into twelve hōrae (hours) and the night into four vigilae (watches) of equal length; how accurately these were measured, however, varied wildly.

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