Zero room for error: Calculating time periods so deadlines aren't missed

Zero. A brilliant mathematical concept. The Romans famously lacked it. I fear we lawyers suffer from a similar failure to appreciate zero's significance.

Words not mathematics are the lawyer’s stock in trade, yet the profession is obsessed with counting. We set time limits by reference to days or years – in limitation periods and notice provisions – and then obsess about counting days to ensure actions are completed on time, or stipulate severe consequences when they are not.

Counting is about as basic as it can be, child's play you might say, but I'm not sure we have grasped where to start.

Consider two formulations for a time limit based on knowledge:

(1) "… proceedings must be started within 30 days beginning with the date when the economic operator first knew or ought to have known that grounds for starting the proceedings had arisen"; and

(2) "The claiming Party shall give a Notice to the Engineer, describing the event or circumstance giving rise to … the Claim … as soon as practicable, and not later than [30] days after the claiming Party became aware, or should have become aware, of the event or circumstance".

The first is the limitation period for procurement claims in Regulation 92(2) of the UK's Public Contracts Regulations 2015 (PCR). Section 106(2) of the recent Procurement Act 2023 adopts similar, but not identical, terms. The second is Sub-Clause 20.2.1 of the FIDIC Yellow Book 2017 (a common international standard form construction contract) but with "30" replacing "28" to make a point.

Common sense suggests that under these formulations time starts running from knowledge (actual or constructive). However, perceived legal wisdom is that the available time period under formulation (2) is one day longer than under formulation (1). How can that be?

The theory goes that under formulation (1), the words "beginning with the date" imply that the date of knowledge must be counted as day 1, whereas under formulation (2) the reference to "after" means that the following day is counted as day 1.

The White Book's guidance on Civil Procedure Rule 2.8 includes the following: "When a step has to be taken within a period described as "beginning with" a specified day, then that day is included in the period; but if the period is described as running "from" or "after" a specified day, then that day is not included in the period".

This reflects a body of case law recognised by the English Court of Appeal in Zoan v Rouamba [2000] EWCA Civ 8 at paragraphs 23 and 24, albeit that it was also acknowledged in that decision that "whether the specified day itself is to be included in, or excluded from, that period" is a question of contract interpretation.

One can hardly quibble with the sentiment that contractual or legislative provisions must be construed according to their terms. However, if the starting trigger (knowledge, in our examples above) for the period is met, surely it would be a conceptual error to exclude from the period any time which follows the trigger (whether the words are "beginning with", "after" or "from").

But maybe the conceptual error is rather a failure to appreciate the significance of zero.

If I wish to use a ruler to draw a line 30cm long, I start not from "1" but from zero. Looked at this way, it makes sense that where a period is expressed to run "from" or "after" an event or date, the day following should be counted as "1"; not because the date of the event is excluded from the period, but because the event represents time zero. Equally, the timeline starts from zero if the period is expressed to "begin with" the event or date. On this view, there is no difference between the periods in formulations (1) and (2).

In Boxxe Ltd v The Secretary of State for Justice [2023] EWHC 533 (TCC), Mr Justice Constable was asked to interpret formulation (1) in an application to lift the automatic suspension in place pursuant to the PCR. It mattered because if the date of knowledge was counted as day 1, the claimant's claim would have been one day out of time; if counted as "day zero", the claim would have been made just in time. Notably, the judge declined the invitation to decide the interpretation point, leaving the matter for trial (which ultimately never took place), despite acknowledging the formidable line of authority supporting counting the date of knowledge as day 1 (a conclusion that, obiter, was viewed sympathetically and as consistent with Zoan in Oracle Security Services Ltd v Barts Health NHS Trust [2024] EWHC 1201 (TCC), a case decided a year after Boxxe).

Whilst commercial parties have no direct control over wording relating to the start of time periods stipulated in statutes, they can and should ensure that such wording in their contracts is crystal clear, particularly where the trigger is knowledge of events, instead of counting on the courts to carry out a far-from-straightforward contract interpretation exercise that may therefore result in a disadvantage to one or both parties.

Authored by Rupert Sydenham and Mark Crossley.