This is a tricky one, as it depends on the type of time limit that has been set.
The deadlines for paying most official fees are set with reference to the European Patent Convention. For example, the filing and search fees must be paid within one month of filing the application. If you file an application on 9 July 2010, the filing and search fees are due on 9 August 2010.
If the due date falls on a day on which the European Patent Office is closed (i.e. at the weekend, or on certain public holidays), the deadline is extended until the next working day. So, using the above example of filing and search fees, if you file the application on 14 July 2010, the fees should be paid by 16 August 2010 (i.e. 14 August 2010 is a Saturday, 16 August 2010 is the next working day).
However, many communications from the EPO also set a deadline for response. This might be a response to an examination report, or a deadline for filing an appeal from an adverse decision. Those communications refer to deadlines using the phrase, “within x months of notification of this communication”. Note that this refers to the date of notification of the communication, not the date of the communication itself. Under the terms of the EPC, notification is deemed to take place 10 days after the date of the communication. The actual date of receipt in that 10-day window is irrelevant, provided that it does in fact arrive. (If it arrives later than 10 days, then work from the date of actual receipt; it would be advisable to inform the EPO of this, though).
So, in these cases, the Applicant usually has a little extra time to respond to the official communication. However, the time limits must be calculated correctly. Notification relates to the receipt of documents from the EPO. Therefore, the 10 days must be added at the beginning of the period for response. Adding the 10 days at the end of the period for response often leads to a different date (and a response that is late filed!). Take an example:
- An examination report is received with a date of 24 May 2010, and a response must be filed “within four months of notification of this communication”.
- Correct deadline: 3 October 2010 (24 May + 10 days = 3 June; 3 June + 4 months = 3 October).
- Incorrect deadline: 4 October 2010 (24 May + 4 months = 24 September; 24 September + 10 days = 4 October)
If you extend the deadline by a number of months, the process for calculating the time limit is the same, but you need to bear in mind that it is the period which is extended, not the deadline. So, take the date of the communication, add 10 days, then add the number of months for response, then add the number of months of the extension, and (only) then extend to the next working day if the EPO is closed on that day.
See also “How do I extend time limits at the EPO?”