The opt-out period - how will it work?

Diagram of the transition timeframe

19 February 2013 – UPC Agreement signed. Ratification period.
Sunrise period. Anticipated mid-2016.
The UPC Agreement enters into force on the first day of the fourth month after the thirteenth ratification (must include GB, FR & DE).
Transitional period, currently 7 years (extendable to 14 years), during which time an action brought against a European patent may be brought in a national court (if opted-out).
Last European patent with SPC expires 25 (20 + 5) years after the patent application date.

The opt-out period – how will it work?