When it comes to giving notice – whether as a landlord or a tenant – the issue of when to send that letter, fax or email can be particularly problematic.

If a period is said to be "30 days beginning with" 1 January, do you count 1 January as day one or not? If "six months' prior notice" is required, does this mean you can only serve notice on the day that falls six months before the event? Thankfully the courts have grappled with these problems, and, generally speaking, common sense has prevailed.

Service "not less than" a specified period before an event

The general rule for these types of clause is that the date of service of the notice is not included, but the date of the event is included. For example, if a notice must be served "not less than" four weeks before it is to take effect and is to take effect on Monday 1 October 2012, the final day on which notice can validly be served is Monday 3 September 2012. As a second example, if notice is to be given "not less than" six months before a date of termination specified within that notice, a notice serviced on 2 April 2012 specifying a termination date of 2 October 2012 would be valid.

Notice to be served on a specified date

"The Tenant may determine the Term on 30 September 2012 by giving the Landlord six months' prior written notice." On the face of it, a clause such as this might suggest that the Tenant can only give notice on 30 March 2012 – the date falling six months before 30 September 2012. In fact, the courts have interpreted this wording as meaning not less than six months' notice must be given.1 In other words, notice can be served prior to or on 30 March 2012.

However, this does not mean that notice could be given at any time before that deadline. In Biondi v Kirklington & Piccadilly Estates Ltd2, the court held that notice must be served a "reasonable time" before the period begins. On the facts of the case, a notice served one month into the term of a 35- year lease, which purported to exercise an option which was exercisable by notice served six months from the end of the term of the lease, was not valid. In Multon v Cordell3, a notice served three years prior to the end of a 35-year lease was also invalid.

Notice to be served within a specified time period

Finally, we turn to clauses stating that notice must be served "ten days after" or "within one month of" a specified date. The general rule is that the date from which the period runs is excluded and the notice may be served right up until the final moments of the last day of the period. So if notice is to be served ten days after 1 October 2012, the final day for service is 11 October 2012, because 1 October itself is ignored for counting purposes.

If the time period is expressed as being a month rather than a number of days, the "corresponding day" rule applies. This means that the date will fall on the same day of the following month, or, if there is no corresponding day, the last day of the month in which the period expires. For example, if otice is to be served within one month from 31 January 2013, it will be due on 28 February 2013 at the latest.

The exception to the general rule above applies to time periods that "commence on" or "begin with" a date. In these cases, the date itself is likely to be included within the computation of the period of time.

Points to remember

Calculating time periods is very important, particularly when dealing with break clauses, in respect of which courts will consider that time is of the essence4.While the points above set out the general position, landlords and tenants should always check for any specific service provisions in the lease, which may override or amend these rules. If notice provisions are not clear, it is possible to serve multiple notices on different days without prejudice to the others. But if you are in any doubt as to when to give notice, the best advice is to do it early.