Laytime disputes: do overlapping exclusions count twice?

Key takeaways

• Distinguish overlapping events from sequential events.
• Establish whether each proposed exclusion applies before calculating its combined effect.
• Avoid subtracting the same elapsed period twice.
• Preserve the separate factual reasons even when the excluded time is combined.
• Present disputed alternatives by assumption rather than hiding them in a total.

Separate the legal question from the interval arithmetic

BIMCO's laytime masterclass treats stoppage as a distinct analytical topic. In an actual fixture, check the current text to determine whether, when and to what extent a proposed exception applies. This article's arithmetic does not determine that contractual issue.

An overlap problem can arise even after the event times have been agreed. The account may contain separate rows for different reasons, each associated with some of the same elapsed time. Adding the durations of those rows can overstate the amount removed from the account.

The first question is factual: do the periods overlap? The second is contractual: which treatment applies to each relevant segment? The third is mathematical: does the calculation implement that treatment without duplication? Keeping these questions separate helps the parties locate the actual disagreement.

Do not merge all reasons into one label merely to avoid the arithmetic problem. The distinct causes may matter to the contractual analysis even where they occupy some of the same time.

Draw the event relationship before taking a total

Represent each material period by a start and end on the same time basis. The relationship will show whether the periods are separate, touching, partly overlapping or fully contained. A list of durations alone cannot reveal that structure.

If one period sits entirely inside another, summing their lengths counts the inner time again. If they overlap only partly, the shared portion creates the duplication. If they are sequential, the durations can be combined without that particular overlap problem, subject to the adopted contractual treatment.

The time basis must be consistent. A period shown in a different zone or without its date can appear separate when it is not. Preserve the original records and explain any conversion before drawing conclusions from the apparent relationship.

Once the structure is clear, divide the review window at the relevant boundaries. Each segment can then be assessed on its actual facts and treatment. This approach is more reliable than subtracting every row labelled “exception” from a grand total.

Worked fictional overlap

This ILLUSTRATIVE example assumes a 36-hour review window. Event A runs from elapsed hour 8 to hour 14, lasting 6 hours. Event B runs from elapsed hour 12 to hour 16, lasting 4 hours. For this example only, both periods are assumed fully excluded under the same simple counting method.

The incorrect method understates counted time by 2 hours because it removes the shared interval twice. The example resolves an arithmetic issue only. It assumes, rather than proves, the applicability of both exclusions and calculates no monetary entitlement.

A live account needs support for the boundaries and the counting assumptions. If either is disputed, the reviewer should preserve the alternatives. The arithmetic should still be correct within each expressly stated scenario.

Identify which disagreement changes the result

The parties may agree that the periods overlap but disagree about whether one exclusion applies. They may agree on both exclusions but disagree about a boundary. Or they may agree on all premises and discover only a duplicate deduction. These are different negotiation subjects.

An issue note should state the disputed premise and the consequence of changing it. A mathematical correction should not be presented as a concession on the contractual question. Conversely, an agreement that a period is excluded should not leave the account's implementation unchecked.

Where a treatment applies only partly or changes during the window, the simple worked example is not a substitute for analysis. Segment the timeline and apply the actual reviewed method. Do not force a more complex arrangement into a full-exclusion model simply because the spreadsheet is built that way.

If the calculation crosses a point where the relevant contractual treatment changes, obtain appropriate advice on the later segments. A reason label carried forward from an earlier part of the account may not establish how the later time should be treated.

Preserve causes while combining time correctly

This table avoids an unhelpful choice between keeping every event separate and merging the whole chronology. The factual record can preserve all relevant causes while the calculation operates on non-duplicated elapsed segments.

The account's explanation should make that distinction visible. A counterparty may otherwise believe that combining the time means abandoning a factual allegation. State that the event evidence remains separate and that the combined duration serves the particular calculation assumption being used.

Resolve the account with a reproducible comparison

When presenting the corrected account, identify whether the change arises from interval arithmetic, a revised boundary or a different treatment. Show the affected segment and reconcile the change in counted time. The recipient should not need to inspect every formula to find the point.

Retain the previously circulated version so the correction can be explained. If the parties are considering alternatives, give each a clear assumption label. Do not call an alternative the final account while its central premise remains unresolved.

The commercial principal should understand the scope of any agreement reached. Accepting a correction for duplicate time may leave a separate dispute about whether the exclusion applies at all. Record the actual agreement and carry any remaining question forward explicitly.

This discipline makes negotiation more focused. Instead of exchanging incompatible totals, the parties can discuss the specific boundary, treatment or mathematical implementation that produces the difference.

Common mistakes

The main error is adding exception durations without mapping their positions in elapsed time. Another is deleting one cause entirely to remove a duplicate deduction. Preserve the factual record while correcting the calculation.

Do not treat a correct union of intervals as proof that the exclusions apply. Avoid mixing differently defined time bases. Finally, explain whether a revised total reflects arithmetic or a substantive position; otherwise, an uncomplicated correction can be mistaken for a wider contractual concession.

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