The Schengen passport rules state that:
If you are a non-EU national wishing to visit or travel within the EU, you will need a passport: valid for at least 3 months after the date you intend to leave the EU country you are visiting, which was issued within the previous 10 years
What I can't find is - does the validity in the first point refer to the expiry date on the passport, or the 10th anniversary of it's issue?
I am a UK citizen, with a passport issued before 2016, when leftover months were added to the new pasport - so mine has an expiry date 10y8m after the issue date. Can I therefore travel to the Schengen zone at, say, 9y10m (at which my passport is less than 10 years old, but still has 10 months remaining), or do I need to renew it prior to 9y9m (so my passport has 3 months less than 10 years since issue when I leave)?
