EPO express
When filing a European patent application the priority period is 12 months, i.e. a full year. Very often you will read or hear the term "priority year", as the right of priority for a patent can be claimed for any date within this time period. The rules of the EPO to calculate a time limit that is expressed in years also apply for the priority year:
When a period is expressed as one year or a certain number of years, it shall expire in the relevant subsequent year in the month having the same name and on the day having the same number as the month and the day on which the said event occurred; if the relevant subsequent month has no day with the same number, the period shall expire on the last day of that month.
Example: You filed your priority application on 29 February 2020. The end of the priority year falls on 29 February 2021. However, as such a date does not exist, the last date when you have to file your subsequent European patent application is the last day of Februar, which in 2021 is 28 February 2021.
A claim to a priority that dates back longer than a year is invalid, except the priority term is extended because the end of the priority term falls on a weekend or any day on which the European patent Office is closed. The EPO publishes the days it is closed in their official journal and on their webite.
Example: if you filed your first application on Thursday, 18 July 2019 then the last day, you have to file any further application to benefit from your right of priority normaly would be 18 July 2020. However, as 18 July 2020 is a Saturday, and the EPO is closed on Saturdays and Sundays, you can file your European patent application on Monday, 20 July 2020 and still benefit from your right of priority.
(c) EPO express 2020
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