"Year" is probably the least problematic expression of time found in a construction or engineering contract. Days, weeks and months constantly feature in disputes.

Time is crucial in construction and engineering contracts.

Everyone is familiar with time as one of the 3 key elements of all projects: time, cost and quality. Great emphasis is placed on the date or period for commencement, completion and maintenance. "On time" is often the high profile, public measure of a project.

More often overlooked is how crucial time, and the expression of time, is in the administration of a project.

Adherence to time periods is required in applications for payment, making payment, in requests for information, the provision of notices, in dispute resolution mechanisms, the computation of damages and more. Adherence to a specified time period requires the calculation of the end of that time period. The calculation gives rise to differences.

When calculating a period of several months or part of a month, is a month four weeks? 30 days? A calendar month? When calculating in weeks, is a week 7 days or is a week 6 working days or 5 business days? Is a "day" any day, a business day, the time between 00:01 hours and 24:00 or any period of 24 hours?

Check your contracts, they will all go some way to addressing these questions in the definitions. For example, borrowed from the FIDIC form of contract, you will probably find a definition for "Day" (defined as "a calendar day" in FIDIC). Though later in your contract you might find reference to "3 working days". What is a "working day"? Does it include Friday? Does it include days over Eid? Is it still a full working day when reduced hours apply during Ramadan?

Why do these distinctions matter? If a time period relates to payment, calculation of the period will be relevant where payment is delayed if the payee is entitled to recover interest or financing charges for the period of the delay. E.g. if "payment is due within 45 days" of application and application is made on 1 December 2014 interest may run from 15 January 2015 (being 45 calendar days later) or 17 January 2015 (allowing for National Day and New Year's Day) or 26 January 2015 (being 45 business days from 1 December 2014).

If the time period relates to the giving of a notice to claim additional time or costs under the contract a contractor might find itself "time-barred".

Perhaps most frequently disputed are the expressions of time used for delay damages. It is not unusual to see reference to a sum, or percentage of the contract sum, payable by a contractor to an employer "per week" the project is delayed. There is a strong possibility the project will not be delayed by a number of whole weeks but actually by a number of weeks and a few days. For example, 15 weeks and 3 days: this can give rise to a dispute as to whether the contractor should pay for only the full weeks the project was delayed, i.e. 15 weeks; or whether the contractor should pay the full damages for every week or part week the project was delayed, i.e. 16 weeks.

The contract might specify that the damages are payable per week or part week pro rata. I.e. in the example above the contractor will pay 15 weeks plus 3/7th of a week. Though this can often give rise to the argument that a week is not 7 days but consists of only 6 working days and therefore the contractor should pay only 15 weeks plus 3/6th of a week. Where delay damages are high, this difference can be worth arguing for. The disputes can be avoided. The calculation of time periods is not difficult but care must be taken not to overlook the definitions and to be consistent in the use of expressions when preparing and administering contracts.

364 or 365 days this year?