If the shop forgets to tell you, you get a year.
The EU Consumer Rights Directive gives you 14 days to withdraw from online and off-premises purchases, counted from the day the goods reach you. If the trader fails to inform you about that right, the deadline stretches by up to twelve months.
Useful: No reason is required – but you pay return shipping if the trader said so up front.
Source: eur-lex.europa.eu