What Year is it? The difference between Sweden and Norway

Norway and Sweden are neighbouring countries and the languages are fairly similiar.

In the year 1999 Norway talked about «nitten nittini» (nineteen ninetynine) or «nitten hundre og nittini» (nineteen hundred and ninetynine), usually using the first version, without using the word hundred.
In Sweden they said «nitton hundra och nitti nio»(nineteen hundred ninetynine) keeping the word hundred.
More or less the same system.

In the year 2000 Sweden continued the system and talked about «tjugo hundra» (twenty hundred), and then «tjugohundra och ett»( twenty hundred and one).
But Norway changed their system radically as the year 2000 became «to tusen» (two thousand) and the next year «to tusen og ett» (two thousand and one).

Two neighbouring countries but two different ways of counting the years.