Mechanical clocks reached close to a peak in precision as early as the end of the 18th century, thanks to research in longitude (the measure of time is then the measure of space). The availability of a great many watches, clocks, and other chronometers during the 19th century for a much wider audience opened the way to innovations in the use of the counting of time. Two developments are studied in this paper. On the one hand, the way time is made public is studied inasmuch as it depends on conventions. However, the standard local time was put in question, whether that of the sun’s course – traditional but irregular – or that provided by mechanical means – regular but far form nature. On the other, the precise calculation of duration became important, as the way the performances of horses in horse racing came to be very precisely measured and accounted for, in an atmosphere of pervasive anglo-mania, testify.