Why on the clock with the Roman numbering write IIII, and not IV

Roman numerals were never used for calculations, but as a number system they were used to designate numbers. Like most numeral systems of Antiquity, the Roman numbers were written on the addition principle, where I = 1, II = 2, III = 3, IIII = 4, V = 5, (...) VIIII = 9, (...) XVIIII = 19, ( ...) XXIIII = 24, we restrict ourselves to examples of numbers that will later be used on the clock to indicate 24 hours a day. During the Imperial period, the principle of subtraction arose, where IV = IIII, IX = VIIII, XXIV = XXIIII, etc. With very few exceptions, this principle based on subtraction was not adopted for official instructions, monuments or a sundial.

Hours (mechanism) measuring hours (time unit) have arisen
at the end of the 13th century. When in the 15th century, watch manufacturers gave this watch a dial, they chose Roman numerals, which by this time were already actively used in sundials. This tradition continued until 1582 and the introduction of the Gregorian calendar. From this point on, the watches on the dials ceased to be divided into 24 hours, but only into 12 sectors.


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Why stayed IIII?

- to balance VIII

- to form three groups of four numbers:

- with I: I, II, III, II

- from V: V, VI, VII, VIII

- c X: IX, X, XI, XII

- so that on both sides of the vertical division of the dial was 14 digits.

An additional reason in favor of IIII is that on the radial dial, on which IIII, V, VI, VII and VIII are marked at an angle downward from the center, IV is read with difficulty.

Notes:
1. translation with reduction (about space did not begin to translate).
2. It appears in the dial using both principles: addition - IIII and subtraction IX
3. On the Kremlin chimes and Big Bene (thanks to tony ) - IV
4. As always, I would be grateful for additions, corrections and clarifications.