6.4. If, at a particular time after 20 December 2002, the taxation year (determined for the purposes of the Income Tax Act (R.S.C. 1985, c. 1 (5th Suppl.))) of a trust or succession is deemed to end, in accordance with paragraph b of subsection 6 of section 249 of that Act and for the purposes of that Act, immediately before the particular time, a new taxation year of the trust or succession is deemed to have begun at the particular time.