A Statement of Facts (SOF) can show a ninety-hour interval between laytime commencement and cargo completion, while the account records only forty-eight hours of laytime and twelve hours on demurrage. The difference comes from the commencement clause, excluded periods and the point at which the allowance runs out.

This guide shows how to turn a port chronology into a calculation that another operator can check. The example is fictional, with every counting assumption stated explicitly.

1. Separate the port record from the counting rules

The SOF records what happened: arrival, notices, cargo operations, stoppages and completion. The laytime statement applies the charterparty to those events. Keep both documents, rather than changing the original SOF to make it match a preferred calculation. BIMCO’s Standard Statement of Facts is an established reference form recommended by BIMCO and FONASBA.

Start a worksheet with one row per uninterrupted interval. Useful columns are start, finish, elapsed hours, event, applicable clause, time counted, cumulative laytime and evidence reference. A short explanation such as “rain stopped loading; clause X applies” is more useful than an unexplained zero.

2. Confirm the commencement point before adding hours

Do not automatically start the calculation at arrival or at the timestamp on the Notice of Readiness (NOR). Check the required arrival place, physical and legal readiness, the recipient and permitted tendering hours, and the notice period. Cargo work before that period expires may have its own counting rule. The Shipowners’ Club guide to laytime and demurrage explains these issues from an English-law perspective.

For your audit trail, record the NOR tender time and the calculated commencement time separately. If readiness or service is disputed, show the competing start times and their financial effect rather than silently choosing one.

3. Worked example: rain, an excluded Sunday and demurrage

Assume the following terms and facts solely for this example:

• A valid NOR is tendered and received on Friday 6 November 2026 at 08:00. The agreed six-hour notice period runs continuously, so laytime starts at 14:00. No earlier work changes that result.
• The loading allowance is 48 hours. All hours otherwise count, but Sundays from 00:00 to 24:00 are excluded even if used.
• The parties expressly exclude the actual hours when rain prevents loading before laytime expires. This is a simplified agreed rule, not a definition of every “weather working day” clause.
• Rain prevents loading on Saturday from 10:00 to 16:00, and again from Monday 22:00 to Tuesday 02:00.
• Loading is contractually complete on Tuesday 10 November at 08:00.
• Demurrage is USD 12,000 per 24-hour day, pro rata. The Sunday and rain exclusions do not apply to demurrage. There is no owner-caused delay or other applicable defence or exception.
• All timestamps use the same local clock, with no time-zone or daylight-saving change.

Original example: event-by-event loading account

Interval	Elapsed	Treatment	Laytime used	Demurrage
Fri 6 Nov 14:00 to Sat 7 Nov 10:00	20 h	Counts	20 h	0 h
Sat 7 Nov 10:00 to 16:00	6 h	Rain excluded	0 h	0 h
Sat 7 Nov 16:00 to Sun 8 Nov 00:00	8 h	Counts	8 h	0 h
Sun 8 Nov 00:00 to Mon 9 Nov 00:00	24 h	Sunday excluded	0 h	0 h
Mon 9 Nov 00:00 to 20:00	20 h	Allowance exhausted at 20:00	20 h	0 h
Mon 9 Nov 20:00 to 22:00	2 h	On demurrage	0 h	2 h
Mon 9 Nov 22:00 to Tue 10 Nov 02:00	4 h	Rain counts on demurrage under assumed terms	0 h	4 h
Tue 10 Nov 02:00 to 08:00	6 h	On demurrage	0 h	6 h
Total	90 h	30 h excluded	48 h	12 h

Demurrage = 12 ÷ 24 × USD 12,000 = USD 6,000.

The cross-check is 90 elapsed hours = 30 excluded hours + 48 hours of laytime + 12 hours on demurrage. The six-hour NOR notice period sits before the table and is not part of its ninety-hour total.

4. Split the account exactly where laytime expires

At Monday 00:00, only 28 hours of the allowance have been used. The remaining 20 hours expire at Monday 20:00. That timestamp is the dividing line between laytime and demurrage.

Deducting all ten hours of rain from the entire port stay would be wrong under our assumptions. Only Saturday’s six hours are excluded. Deducting Monday night’s four hours as well would incorrectly reduce demurrage to eight hours, or USD 4,000.

The BIMCO Laytime Definitions for Charter Parties 2013 distinguish laytime exceptions from demurrage and give different formulations for weather working days. Those definitions are intended for express incorporation. Read the actual wording before choosing a weather deduction method or applying a laytime exclusion after expiry.

5. Make the calculation easy to audit

• Avoid overlapping deductions. If rain falls during an already excluded Sunday, label both events but do not subtract the same hour twice.
• Reconcile the clock. Record dates, local time and any UTC offsets. Resolve mismatches between agent, terminal and vessel records before calculating durations.
• Keep minutes until the final step. Twelve hours thirty minutes is 12.5 hours, not 12.30 hours. Round money according to the contract or agreed settlement method.
• Link every adjustment to evidence. Use SOF entries, logs, notices and relevant correspondence. Flag uncertain intervals separately.
• Check the contractual endpoint. The last tonne moving, completion of securing and departure need not be the same event.

6. Keep claim deadlines separate from the arithmetic

A correct total does not establish that a claim was presented properly. Check the charterparty for the notice deadline, documented-claim deadline, required recipient and specified supporting documents. There may be more than one deadline. Steamship Mutual’s demurrage time-bar FAQ explains why the precise wording matters.

Prepare a package containing the calculation, contractual basis and relevant supporting records, then check it against the actual clause. A generic checklist cannot replace a contract-specific document requirement.

Common questions

Does every stoppage in the SOF stop laytime?

No. A stoppage is a fact to classify. Whether its duration counts depends on the agreed terms and the circumstances. Keep the event and the contractual treatment in separate columns.

Can I enter the full port stay into a basic calculator?

Only if its calculation matches the agreed counting rules. First establish commencement, permitted deductions and expiry. Our Laytime Calculator can help check simple elapsed-time and rate arithmetic, but its basic start/end inputs do not resolve NOR validity, weather clauses or claim deadlines.

This article is an educational example, not legal advice. Actual entitlement depends on the charterparty, incorporated definitions, evidence and governing law. Seek qualified advice on disputed terms or time bars.