Modulation Day or RTT: What the Court of Cassation Has Ruled for Your Paid Leave

You work in Saint-Amand-Montrond for a company that organises work in cycles, with modulation days added to RTT days (reduction of working time). One day, you take leave and, when settling it, your employer tells you that the last day of your leave — which falls on a modulation day — is not counted as a paid leave day. Result: you lose a rest day. You wonder: is this legal?

The answer is no, according to a ruling of the Court of Cassation of 29 January 2020. The judges clarified a subtle but crucial distinction between two concepts: modulation days (which serve to distribute working hours over a cycle) and RTT days (which are the counterpart of work beyond 35 hours). When paid leave ends on a modulation day, the latter must be counted as a leave day. This decision, which went relatively unnoticed, has concrete consequences for thousands of employees.

In this article, I will tell you the story of this case, dissect the reasoning of the magistrates, and then give you practical advice to check your own pay slips. Because, believe me, I have seen too many cases where employees were deprived without knowing it.

The facts: a story that happens every day

The case pits an employee, Mr X., against his employer, the association Hôpital Saint-Camille. Mr X. works in a healthcare establishment where working time is organised in cycles, with so-called 'modulation days' — days when the employee does not work, but which are not RTT days. In short, the company distributes working hours over a period (for example over a 4-week cycle) and certain days are 'modulated' to balance working time. These modulation days are different from RTT days, which are granted in compensation for actual work beyond the legal duration of 35 hours per week.

Mr X. takes paid leave. When his leave ends, the last day of his leave falls on a modulation day (a day he would not normally have worked). The employer refuses to count that day as a paid leave day, on the grounds that the modulation day is not a working day and therefore cannot be 'consumed' as leave. For the employer, paid leave must be counted in working days (all days of the week except Sunday and public holidays), and a non-working day (like a modulation day) cannot be charged to leave.

Mr X. contests. He brings the matter before the employment tribunal, then the court of appeal, and finally the Court of Cassation. His argument: the modulation day is a working day (because it is neither Sunday nor a public holiday), so it must be counted in the calculation of leave. The employer retorts that the modulation day is 'non-working' by nature and cannot be used as a leave day. The case bounces back: the court of appeal rules in favour of the employer, but the Court of Cassation quashes the decision and refers the case to another court of appeal.

The reasoning of the court — dissected

The Court of Cassation relies on Articles L. 3141-1 et seq. of the Labour Code (which define paid leave) and on the concept of 'working days'. According to the law, the calculation of leave in working days includes all days of the week except Sunday and public holidays. But the question is: is a modulation day a working day? The answer is yes, because it does not fall on a Sunday or a public holiday. The Court goes further: it distinguishes the nature of modulation days and RTT days. RTT days are the counterpart of work performed beyond 35 hours; they are assimilated to work time not performed but paid. Modulation days, on the other hand, are 'low' days in a cycle: they do not remunerate an excess of hours, but simply organise the distribution of work. They therefore do not have the same nature.

The judges consider that, in the context of a calculation in working days, when the last day of leave coincides with a modulation day, that day must be counted as a paid leave day. Why? Because the employee is entitled to a certain number of leave days, and those days must actually be taken. If the employer excludes modulation days from the calculation, the employee loses a rest day. However, the law wants leave to be effective. The Court of Cassation thus validates an interpretation favourable to the employee, recalling that modulation days are not RTT days and cannot be assimilated to non-working days.

This ruling is a confirmation of earlier case law (Cass. soc., 13 April 2016, No. 14-28.293) which had already distinguished RTT days from other non-working days. It is therefore not a reversal, but a useful clarification. The Court specifies that the solution would be different if the calculation were in business days (days actually worked): in that case, a modulation day would not be counted, because it is not a usual working day. But in working days, a modulation day is a day like any other.

What this means for you — concretely

If you are an employee of a company that uses work cycles with modulation days, this decision directly concerns you. Concretely, if you take paid leave and the period includes a modulation day (or your last leave day falls on a modulation day), your employer must count that day as a leave day. He cannot tell you: 'On that day, you wouldn't have worked anyway, so it's not leave.' No: that day counts towards your 30 working days (or 25 business days) of annual leave.

Let's take a concrete example: in Mehun-sur-Yèvre, a clinic organises work in cycles of 4 weeks with 2 modulation days per cycle. You take 2 weeks of leave (12 working days). If the last day of your leave falls on a modulation day, you will have consumed 12 leave days, not 11. If the employer refuses, you lose a rest day that you could use later. Over a year, this can represent several lost days.

For employers, the rule is clear: when calculating leave in working days, do not exclude modulation days. Otherwise, you expose yourself to employment tribunal litigation for leave arrears. Damages can reach several hundred euros per day not granted.

If you are a trade unionist or staff representative, this case law is a tool to negotiate company agreements on working time. You can require that the modalities of leave calculation be specified in the internal regulations or collective agreement.

Four tips to avoid this type of dispute

• Check your leave calculation method: working days or business days? Look at your pay slip or contract. If it is in working days, modulation days must be counted.
• Keep your schedules and work cycles: in case of a dispute, you must prove that a modulation day coincided with your leave. Ask your employer for a copy of the work cycle organisation.
• Do not hesitate to put the question in writing: if your employer refuses to count a modulation day as leave, send him a registered letter with acknowledgement of receipt to obtain a written response. This will constitute evidence.
• Consult a lawyer specialising in labour law: if the amount at stake is significant (several lost leave days), an employment tribunal action may be worthwhile. The procedure is free before the employment tribunal, but a lawyer will help you structure your claim.

Further reading: related case law and developments

This decision is part of a consistent line of case law. Already, in a ruling of 13 April 2016 (No. 14-28.293), the Court of Cassation had held that RTT days could not be imposed as leave days. The logic is similar: modulation days and RTT days have distinct legal natures. More recently, the Court confirmed this approach in a ruling of 10 November 2021 (No. 19-24.681), specifying that rest days granted under a fixed-term contract are also not assimilable to paid leave.

The trend is therefore towards enhanced protection of employees' leave rights. The courts ensure that working time adjustment schemes (cycles, modulation, fixed-term contracts) are not used to reduce the effective number of leave days. In the future, we can expect judges to be even stricter, particularly in the case of vague clauses in collective agreements or company agreements.

For HR professionals and lawyers, this ruling is a reminder: the drafting of agreements on working time must be precise. It is recommended to include an explicit clause on the calculation of leave in the presence of modulation days, in order to avoid litigation.

Summary and next steps

FAQ:

1. What is a modulation day? It is a non-working day within the framework of a work organisation by cycles, which allows the distribution of working hours over a period. It is not the counterpart of overtime.
2. Can a modulation day be counted as a leave day? Yes, if the calculation of leave is in working days. It must be included in the calculation of the number of leave days taken.
3. What if my employer refuses? Gather your evidence (pay slips, schedules) and send him a registered letter. If the refusal persists, bring the matter before the employment tribunal.
4. Does this rule apply to RTT days? No, RTT days have a different nature. They are the counterpart of work exceeding 35 hours and are not counted as working days in the calculation of leave.
5. What is the time limit to act? You have 2 years from the date you became aware of the dispute (for example, the employer's written refusal). After this period, your action is time-barred.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →