Story Behind New Years Day

i have always wondered the story behind the chant Hark now hear,The Cardiff sing, And Swansea run away, AGAIN! And we will fight forever more, Because of New Years Day... could somebody tell me the story of this new years day please

as I recall it started way back when we played swansea on New Years Day in 1980. It was the first ime we had played them for many years and, despite outplaying them (I know, I was there!) they scored a last minute goal to beat us 2-1

And one of our lot shaged their mascott onn the side of the pitch