The UKIPO has changed its practice on calculating opposition periods. Previously, all terms for responding in trade mark opposition proceedings were calculated as full months, eg 1 January 2010 to 1 March 2010. Now, the opposition period will be one day shorter, because it will be calculated on the basis of calendar months. So where a UK trade mark application is published on 4 March 2011, the two month opposition period will expire on 3 May 2011, not 4 May 2011. Similarly, an application to extend the opposition period by a third month must be filed by 3 May 2011.
However, other periods are still calculated as full months, including the term for filing a counterstatement and the nine month cooling off period. But in both cases, if a trade mark is published on the 31st of a month, and the deadline falls in a shorter month, the deadline will be on the 30th of that month (or the 28th/29th in the case of February). For example, if an opposition is served on 31 July 2011, the deadline for filing the counterstatement would be 30 September 2011.
Trade mark practitioners and potential opponents need to be aware of this change, to avoid missing critical deadlines.