For the five continuous years they can be any five years.
However, they must be continuous.
As long as you can supply proof for five continuous years out of the seven, you will not have to provide proof for the other two years.
So, the five years from the seven, assuming the exercising of Treaty Rights began on 1 June 2004, could be, (as examples):
1 June 2004 - 31 May 2005
1 June 2005 - 31 May 2006
1 June 2006 - 31 May 2007
1 June 2007 - 31 May 2008
1 June 2008 - 31 May 2009
But you could also choose:
1 June 2006 - 31 May 2007
1 June 2007 - 31 May 2008
1 June 2008 - 31 May 2009
1 June 2009 - 31 May 2010
1 June 2010 - 31 May 2011.
You CANNOT do this:
Exercised treaty rights:
1 June 2004 - 31 May 2005
1 June 2005 - 31 May 2006
Not exercising Treaty Rights for 2 years, then:
1 June 2008 - 31 May 2009
1 June 2009 - 31 May 2010
1 June 2010 - 31 May 2011.
In this case the clock would go to zero after 2006. You would have a maximum of three continuous years of exercising treaty rights (2008 - 2011), so would have to wait till 2013 to complete five continuous years of exercising treaty rights
i.e.
1 June 2008 - 31 May 2009
1 June 2009 - 31 May 2010
1 June 2010 - 31 May 2011
1 June 2011 - 31 May 2012
1 June 2012 - 31 May 2013
For more details see Chapter 6 of UKBA's information on PR :
http://www.ukba.homeoffice.gov.uk/sitec ... iew=Binary