I was wondering about the date of expiry on my UK passport. Isn't the normal validity period 10 years? Mine was issued on 01 Apr 2012 but the expire date is 01 Sep 2022.
If you had a passport prior to the one that you currently hold and renewed it early then up to 9 months validity can be added to your new passport.
You can renew your passport at any time. When you renew your passport, time left on your existing passport is added to your new one, up to a maximum of 9 months.
So if you had a passport that was valid from September 2002 to 2012, but renewed your passport in April 2012 the new one would be valid until September.