Laytime Calculation: Where the Hours Actually Go

A voyage charter gives the charterer a fixed period to load and discharge. Use less and the owner may owe despatch. Use more and the charterer owes demurrage. Between those two outcomes sits a calculation that is arithmetically simple and legally treacherous, and most disputes turn on which hours counted rather than on how the addition was done.

The Laytime Definitions for Charter Parties 2013 define laytime as the period of time agreed between the parties during which the owner will make and keep the vessel available for loading or discharging without payment additional to the freight. Demurrage is defined as an agreed amount payable to the owner in respect of delay to the vessel once the laytime has expired, for which the owner is not responsible.

Those two sentences contain the whole commercial structure. What follows is how the hours get counted, where they stop counting, and why a general exceptions clause almost certainly does not help you.

The Definitions Only Apply If You Incorporated Them

Start here, because it catches people out.

The Laytime Definitions for Charter Parties 2013 were adopted by BIMCO's Documentary Committee in Paris in May 2013 and endorsed by the Baltic Exchange, the Comité Maritime International, and FONASBA. They replaced Voylayrules 1993, which had itself replaced the 1980 Charterparty Laytime Definitions.

The 2013 revision made a deliberate change of approach. Voylayrules had been issued as a self-standing code of rules that departed in several respects from accepted principle and practice, and its limited uptake was attributed to exactly that. The 2013 version was restored to the original 1980 concept of definitions rather than rules, drafted to reflect contemporary market understanding based on the current state of English law.

The critical feature is the preamble. The definitions apply for the purposes of laytime only, and only when expressly incorporated into the charter party. Parties can incorporate the whole set or identified provisions.

If your charter does not incorporate them, the words in it mean whatever English law says they mean, which is generally similar but not identical, and the gaps get filled by case law rather than by a published definition.

The Day Types

The unit of laytime is defined by the charter, and the choice moves substantial cost between the parties.

Running days, also called consecutive days, means every calendar day counts. Weekends, holidays, nights, all of it. This is the least favorable formulation for the charterer and is common in tanker charters where port operations run continuously.

Working days count only days on which work is normally carried out at the port under local law or practice. The 2013 definitions brought this into line with English law. Local custom therefore determines the answer, which makes the operating practice at a specific port a contractual question rather than an operational detail. A port where Saturday is a normal working day treats it differently from one where it is not.

Weather working days is where the drafting matters most, and where the 2013 revision made its most significant correction.

Voylayrules 1993 had combined three variations of weather working day into a single rule. That was reversed. The 2013 definitions give separate meanings to the different formulations, including a distinct definition for a weather working day of 24 consecutive hours.

The distinction is not academic. A weather working day is a day on which work would normally be carried out and on which weather permits it, with time deducted according to how the definition is framed. A weather working day of 24 consecutive hours treats the day as a continuous block. The two produce different answers on the same facts, and the difference on a multi-day weather event can run to a full day or more of laytime.

If your charter says weather working days without more, you have not specified which of the three you meant, and the 2013 definitions exist precisely to resolve that ambiguity for parties who incorporate them.

Calendar days and running hours or consecutive hours complete the set. Running hours was added in 2013 to reflect practical usage.

Sundays, Holidays, and the Modifiers: The day type is then modified.

SHINC, Sundays and holidays included, counts them. SHEX, Sundays and holidays excluded, removes them. At a port with frequent religious or national holidays, SHEX can hand the charterer several days of free time that the owner absorbs. FHEX does the same for Fridays and holidays in ports where Friday is the rest day.

The exclusions are then qualified further by phrases such as even if used and unless used. Even if used excludes the period from laytime whether or not the charterer worked. Unless used counts the time actually worked. Some forms add unless used, in which case only time actually used to count, which produces a third result.

The 2013 definitions deliberately avoid abbreviations, using them only for WIBON and WIPON, on the basis that many acronyms have no generally accepted meaning and are capable of more than one interpretation. That is a caution worth taking seriously. A fixture recap full of acronyms is a dispute waiting for a trigger.

Reversible Laytime and Averaging

Most charters allocate separate laytime for loading and discharging.

Reversible laytime pools both allowances into one total. Six days for loading and four for discharging on reversible terms gives the charterer ten days across both operations. Time saved at the load port carries forward.

Averaging works differently. The parties calculate each port separately and then set time saved at one against time lost at the other. The results differ, and a charter that says the laytime is to be averaged is not saying the same thing as one that says it is reversible.

Where the Clock Starts

Laytime does not begin because the vessel arrived. It begins when a valid Notice of Readiness has been tendered and any contractual notice period or turn time has run.

We covered NOR validity in detail separately, and the short version is that the vessel must be an arrived ship, physically ready, and legally ready, and the notice must be given by a permitted method at a permitted time. An invalid NOR is a nullity and laytime does not commence.

Two further definitions from the 2013 set matter here.

WIBON, whether in berth or not, and WIPON, whether in port or not, permit NOR to be tendered before the vessel has reached the berth or the port respectively. Under a berth charter, a vessel that cannot reach the berth is not an arrived ship, so these provisions transfer congestion risk to the charterer by allowing the clock to start anyway.

Always accessible goes further. The 2013 definition provides that the charterer undertakes an available berth be provided on arrival which the vessel can reach safely without delay, and additionally undertakes that the vessel will be able to depart safely and without delay at any time before, during, or on completion. That second limb was a deliberate addition and it converts always accessible into a warranty covering departure as well as arrival.

The 2013 definitions also address the waiting place problem. Where a vessel is unable to berth but cannot tender NOR at a waiting place, time lost counts against laytime or, on expiry, as demurrage. Once a berth is available, laytime or demurrage ceases to count until the vessel is at a place where NOR can be tendered.

Interruptions Are Not the Same as Exceptions

This is the distinction that decides most calculations, and it is worth stating precisely.

An interruption is a period that falls outside the definition of laytime in the first place. If the charter provides for weather working days, time when weather prevents work is not laytime at all. It never started counting. The same is true of a Sunday under SHEX terms.

An exception is a period that would otherwise count as laytime but which a clause removes. A strike clause providing that time lost through strikes shall not count is an exception.

The practical difference is the burden and the drafting. An interruption follows from the definition of the laytime unit. An exception requires a clause that clearly covers the event, and the courts construe those clauses strictly.

General Exceptions Clauses Do Not Apply to Laytime

Here is the point most charterers get wrong, and it is settled.

It is generally accepted that general exceptions clauses do not apply to laytime or demurrage.

Most charter parties contain a broad exceptions clause listing perils of the sea, acts of God, restraint of princes, and similar. Charterers routinely assume that clause protects them against laytime running during such an event. Under English law it does not. To interrupt or except laytime, the clause must be directed at laytime specifically and must clearly cover the event.

The implication for drafting is direct. If you want strikes, port closures, weather beyond the day-type definition, or congestion to stop the clock, the charter needs a laytime exception saying so. A general exceptions clause elsewhere in the document will not be read across.

WIBON Starts the Clock and Does Nothing Else

The interaction between WIBON and exception clauses produced one of the more instructive recent decisions.

In Carboex SA v Louis Dreyfus Commodities Suisse SA [2011] EWHC 1165 (Comm), four vessels were fixed under a contract of affreightment on the AMWELSH form to carry cargo to Spain. They arrived shortly after a nationwide haulage strike had ended, but congestion caused by the after effects of the strike persisted. Clause 9 provided that in case of strikes, lockouts, civil commotions, or any other cause beyond the control of the charterers which prevent or delay the discharging, such time was not to count unless the vessel was already on demurrage.

The charter was a berth charter with a WIBON provision, so the vessels could tender NOR notwithstanding the congestion, and laytime commenced.

Owners argued that the WIBON provision placed the risk of congestion on charterers, so that only delay from a strike actually in progress after berthing was excluded. Since the strike had ended before the vessels berthed, nothing fell to be deducted.

Field J rejected that. The court held that the meaning of an exceptions clause is determined without regard to the fact that, by virtue of WIBON, the charterer would otherwise bear the risk of delay in berthing due to congestion. WIBON is a free-standing provision whose function is to enable the laytime clock to start. It has no further effect and does not bear on the construction of the exception. The strike exception therefore covered delay caused by congestion resulting from the after effects of a strike that had already ended.

The Court of Appeal upheld that in June 2012. The reasoning drew on the earlier authorities, including The Amstelmolen, where a vessel unable to berth because of congestion was held to have laytime running by virtue of WIBON while an obstruction within the strike clause meant that time did not count, and Reardon Smith Line Ltd v East Asiatic Co Ltd [1938] 4 All ER 107.

The takeaway for both sides is that WIBON transfers congestion risk only in the sense of starting the clock. It does not immunize the owner against exception clauses that stop it again.

Owner's Fault

Laytime does not run during delay caused by the owner or the vessel. That principle is separate from any exception clause and it does not require one.

Where the vessel is unable to perform the service required of her, the owner is in default of the obligation to perform, and time attributable to that default does not count against the charterer. The analysis applies even where the cause was a latent defect that the owner could not have foreseen, because the question is whether the vessel performed rather than whether the owner was blameworthy.

This is the provision that makes accurate contemporaneous records matter. A charterer challenging a demurrage claim on the basis of owner's fault needs evidence of what the vessel was doing and when, and that evidence lives in the statement of facts, the deck log, and the pumping records.

Building and Checking the Calculation

The mechanics are straightforward once the legal questions are settled.

Establish the NOR tender time and confirm the notice was valid. Apply any notice period or turn time. Identify the moment laytime commenced. Apply the day type to each period. Deduct interruptions arising from the day-type definition. Deduct exceptions where a clause clearly covers the event. Continue until the allowance is exhausted, at which point demurrage begins and, subject to narrow exceptions, runs continuously.

The documents that support it are the NOR, the statement of facts signed by all parties, the vessel's log extracts, pumping logs where applicable, letters of protest, and any port authority or weather records relied on for interruptions.

Two practical points determine whether a calculation survives challenge.

The statement of facts is the evidence. A statement of facts signed without qualification records the agreed timeline. A disputed entry needs a note at the time, not a reconstruction later.

Weather deductions require weather evidence. Asserting that weather prevented work is not the same as proving it. Independent port or meteorological records are what make a weather working day deduction stand up.

What to Do About It

For Owners: Incorporate the 2013 definitions expressly and specify which weather working day formulation applies. Keep contemporaneous records that support the laytime statement rather than assembling them when the claim is prepared. Watch the demurrage time bar, which we covered separately and which extinguishes more claims than any substantive defense.

For Charterers: Do not assume the general exceptions clause protects you. If you want an event to stop the clock, negotiate a laytime exception that names it. Understand that WIBON starting the clock is a separate question from whether an exception stops it, and that Carboex leaves you room to argue the second even where the first is against you.

For Both: Review the acronyms in your recap. The 2013 definitions avoid abbreviations because most of them have no settled meaning, and a fixture agreed by shorthand is a fixture where the parties may have agreed different things.

The Bottom Line

Laytime is arithmetic wrapped around contract interpretation. The addition is easy. The questions that determine what gets added are the day type, the modifiers, whether an event is an interruption or an exception, whether the exception clause covers it, and whether the delay was the owner's fault.

Those questions are answered by the words in the charter party, and they are answered before the vessel sails rather than when the claim arrives. The parties who do well in demurrage disputes are generally the ones who read the laytime clause at fixture rather than at recap.