Teacheranne as I understand it you can apply to renew a passport from nine months before it expires, and those months will be allowed for so that the expiry date on the new passport is ten years after the existing one expires.
The issue date is when the new passport is actually issued.
Some airlines and countries require six months left from this earlier date, so potentially you lose the last three months before the expiry date.
An example:
Original passport expires in November 2010.
Application to renew can be submitted from February 2010.
Issue date on new passport will say February 2010.
Expiry date on new passport will say November 2020.
Some airlines and countries however will only allow travel up to August 2020.
This is what had happened to the lady I sat with on Tuesday.
Ryanair, despite their system allowing her to check in and print her boarding pass, refused to let her fly. The first she knew was at the airport.
Jet2 were happy to let her fly.