The road to enduring reform is littered with the corpses of discarded utopian ideas. So it was with the gradual shaping of the French Republic in the wake of the Revolution. Alongside the political motto ‘Liberty, Equality, Fraternity’, the decimalisation of currency and the adoption of the metric system, another radical endeavour emerged in the wake of 1789. Four years later, the French Republic attempted to reshape the experience of time by instituting a new calendar for a new age and a new humanity.

The aim of the French Republican calendar was to formalise a complete break with the past of the ancien régime, with religion, and with kings. On 22 September 1792, after the Convention decreed the abolition of the monarchy, Jacques-Nicolas Billaud-Varenne, a close ally of Danton and Robespierre, required that henceforth all acts of the Convention be dated Year I of the French Republic. From January 1793, the Convention accordingly stopped recording the ‘vulgar era’ – the age of tyranny – and its members turned their attention to creating a new way of measuring time, fit for a regenerated France.

As part of the wider project of the Comité d’instruction publique responsible for devising schooling for the masses, Charles-Gilbert Romme, a mathematician and agronomist, was tasked with forging a new calendar. The moral, social and political values of the Revolution were to be translated into the dimension of time itself, marking a great reset for humanity. The calendar would replace the popish Gregorian calendar, steeped in obscurantist religious tradition; it would instead be shaped by reason.

Romme and his committee did away with the names of saints, the Christian feast days and the seven-day week ending with Sunday, the day of rest. Instead, the year was divided into 12 months of 30 days and each month into three sequences of 10 days known as decades. Each day lasted 10 hours, each hour 100 minutes and each minute 100 seconds, so that each day was made up of 100,000 tiny little parts, which Romme said corresponded to the pulse of a man of average height, in good health, marching on the double.

The focus on symmetry, in harmony with the adoption of the metric system, expressed the scientific framing of the calendar project, devised by Romme in collaboration with two surveyors, Joseph-Louis Lagrange and Gaspard Monge, and an astronomer, Alexandre-Guy Pingré. Together they attempted to align their symmetrical division of time with the movements of the stars. The first day of the year in the new calendar was set on the day of the proclamation of the new regime, which happened to be the autumn equinox as measured by the Paris Observatoire. ‘Thus’, Romme wrote, ‘was equality between days and nights written in the sky just at the moment when civic and moral equality was proclaimed by the representatives of the French people as the sacred foundation of its new government.’

But what should the new divisions of time be called? Romme had initially suggested references to Revolutionary events, goals and means, in order that the calendar should guide the thoughts and actions of citizens. Months might bear the names of ideals like Fraternity and Justice or of foundational events such as the fall of the Bastille; the days of the decade might be given symbolic names such as Hat (the red phrygian hat, symbol of liberty), Cockade (displaying the three colours of the Republic), or Pike (the weapon of the free man).

But all these references were specific to France, and the Revolutionaries intended the calendar to mirror the values of the Enlightenment and to be universally applicable to all the peoples of the earth. Besides, the Revolution wasn’t over. There might be new historical summits, new glorious names, new symbols to honour. In consequence, and because they could be found in the natural world and were understood by all peoples, numbers were chosen in preference to Republican symbols, in a decree which the Convention dated the 14th day of the first month of Year II.

But an exclusive reliance on the names of numbers seemed rather prosaic and drab. And on the third day of the second month of Year II, an alternative approach was adopted. This was the work of actor and poet Philippe François Nazaire Fabre, known as Fabre d’Églantine, who had joined the Revolution out of a yearning for a new patriotic theatre and poetry that would help establish equality and fraternity, and proposed to use poetic language in the new calendar to promote Revolutionary ideology.

In his report, Fabre d’Églantine offered to substitute ‘for visions of ignorance the realities of reason, and for sacerdotal prestige, the truth of nature’. This was an Enlightenment project that embraced Rousseau’s exaltation of the idea of nature, and Fabre d’Églantine worked with the assistance of André Thouin, gardener at the Jardin des Plantes of the Muséum National d’Histoire Naturelle in Paris, ‘marking the days and the divisions of the year with intelligible or visible signs taken from agriculture and rural life’.

Fabre d’Églantine’s came up with new names for the months expressive of the weather, the season and the things that grow at different times of year. The first three months of the calendar – spanning autumn – are Vendémiaire, echoing vendanges, the harvesting of the vine; Brumaire, from brume, or mist; and Frimaire, from frimas or frost. These are followed by Nivôse, Pluviôse, Ventôse in the winter, Germinal, Floréal and Prairial in the spring and in the summer, Messidor, Thermidor and Fructidor. Each day of the year was also allocated, instead of a saint, a natural symbol taken from the names of animals, fruit, vegetables and flowers, and agricultural tools. Amid the pastoral poetry, some ideological points were made: the 25th of December, which the Revolution no longer acknowledged, and which now fell on the 5^th of Nivôse, became the day of the dog.

The next challenge was to roll out the use of the new calendar to the entire country. In Hilary Mantel’s novel about the French Revolution, A Place of Greater Safety, Camille Desmoulins is given the line: ‘January is abolished, goodbye to aristocratic June. People will ask each other, “What’s today in real days?”’ Though Romme and his fellow scientists compiled an almanac to help country people understand the new system, they came up against the fact that even after the Revolution the French remained as they had been – a people profoundly shaped by customs and a collective memory transmitted from generation to generation. In the countryside especially, though there were pockets of adoption, by and large people continued to cleave to the traditions and rhythms that had shaped their lives.

The first reform of timekeeping to be abandoned was decimalisation, suspended ‘indefinitely’ by the Convention on 18 Germinal Year III (7 avril 1795) during a period of reaction immediately following the Terror, when many symbols associated with Year II and its wave of vandalism and violence – the pike, the red Phrygian cap, the bellicose Carmagnole dance – were jettisoned. France settled into a double way of thinking about the calendar: it was strictly implemented in government and administration as a symbolic confirmation of the permanent abolition of the monarchy. But almanacs and the press operated a dual system of dating, old and new.

This compromise endured until 1804, the year of Napoleon’s coronation. During the first year of the Empire, while French time continued to be dated from 1st Vendémiaire in Year I, the Emperor realised that in spite of its universalist mission the Revolutionary calendar had had the effect of isolating France from the rest of Europe. The Senate voted its abolition on 9 September 1805 (22nd Fructidor Year XIII), and from 1st January 1806 – after a hiatus of 13 years – France returned to the Gregorian calendar.

The experiment of the French Republican calendar crystallises a dream of rationality and symmetry that has found other expressions in French culture and society, from the geometric designs of French gardens to the introduction of the metric system. The calendar, a hybrid of political ideology and late-18th-century neo-classical pastoral, did not last in the face of pragmatism and attachment to tried-and-tested traditions and practices. And like many other French Revolutionaries, the architects of the calendar came to be seen as enemies of the regime. Fabre d’Églantine was guillotined; Romme stabbed himself to death while awaiting execution.

The memory of the experiment lingers in France in the form of the quaint and charming names invented for the months, belying the radical ideology that underpinned it. In the 20th century, the utopian desire for a great reset would draw inspiration from the French Revolution’s conceit of Year I, notably at the hands of the Khmer Rouge, most of whose leadership were French-educated communists. 1975 marked Year Zero for Cambodia, when the desire to bring about a new regenerated culture by eradicating the country’s history, culture and traditions led to an estimated death toll of thre million people.