Needed a third with both
It can be written either way
IV, iv, IIII or iiii for four,
IIII or IV?
The notation of Roman numerals has varied through the centuries. Originally, it was common to use IIII to represent "four", because IV represented the god Jove (and later YHWH). The subtractive notation (which uses IV instead of IIII) has become universally used only in modern times. For example, Forme of Cury, a manuscript from 1390, uses IX for "nine", but IIII for "four". Another document in the same manuscript, from 1381, uses IV and IX. A third document in the same manuscript uses both IIII and IV, and IX. Constructions such as IIIII for "five", IIX for "eight" or VV for "ten" have also been discovered. Subtractive notation arose from regular Latin usage: the number "18" was duodeviginti or “two from twenty”; the number "19" was undeviginti or “one from twenty”. The use of subtractive notation increased the complexity of performing Roman arithmetic, without conveying the benefits of a full positional notation system.
Likewise, on some buildings it is possible to see MDCCCCX, for example, representing 1910 instead of MCMX - notably Admiralty Arch in London. Another notable example is on Harvard Medical School's Library which reads MDCCCCIIII for 1904.
Calendars and clocks
Clock faces that are labelled using Roman numerals conventionally show IIII for 4 o'clock and IX for 9 o'clock, using the subtractive principle in one case and not in the other. There are several suggested explanations for this, several of which may be true:
The four-character form IIII creates a visual symmetry with the VIII on the other side, which IV would not.
The number of symbols on the clock totals twenty I's, four V's, and four X's, so clock makers need only a single mold with five I's, a V, and an X in order to make the correct number of numerals for the clocks, cast four times for each clock:
V IIII IX
VI II IIX
VII III X
VIII I IX
IIX and one of the IX's can be rearranged or inverted to form XI and XII. The alternative uses seventeen I's, five V's, and four X's, possibly requiring the clock maker to have several different molds.
IIII was the preferred way for the ancient Romans to write 4, since they to a large extent avoided subtraction.
It has been suggested that since IV is the first two letters of IVPITER, the main god of the Romans, it was not appropriate to use.
The I symbol would be the only symbol in the first 4 hours of the clock, the V symbol would only appear in the next 4 hours, and the X symbol only in the last 4 hours. This would add to the clock's radial symmetry.
IV is difficult to read upside down and on an angle, particularly at that location on the clock.
Louis XIV, king of France, preferred IIII over IV, ordered his clockmakers to produce clocks with IIII and not IV, and thus it has remained