Bill learned to ski as soon as he could walk, and this was no surprise as his parents managed the Chalet at Charlotte Pass, in the Snowy Mountains. He didn’t have much of a technique when he first started skiing, but hard training meant that soon enough he was able to beat his father - that happened in one of his first competitions in Thredbo. In 1948, at the age of 13, he competed in the National Championships and also in Interstate Team Competitions at Mount Hotham, before winning his first important race the following year, a Slalom at the NSW Championships. This was to become his favourite alpine discipline.
 
In 1951 Day was selected in the team that represented Australia in the Inter-Dominion Championships, a competition held in New Zealand and Australia. After winning a qualification event in Australia, Bill made the Australian Team for the Oslo 1952 Winter Olympic Games. at the age of 17. This was to be his first time representing Australia overseas.
 
Day attributes his ski racing success to his Austrian coach, Leonhard Erharter. Erharter was appointed as a coach for the Australian Winter Olympic Team in the 1950’s and had a long career as the head ski instructor at Thredbo. Under his tutelage, Bill Day went on to win numerous National titles, scoring podium results at the Inter-Dominion Championships and representing Australia at the Olympics two more times, at Cortina D' Ampezzo 1956 and at Squaw Valley 1960. In California Day became the first Australian Winter Olympian to participate in three consecutive Winter Games. With a 52nd place in the Downhill and a 41st in the Giant Slalom, it was that performance at his third and last Olympics that Bill was most proud of.
 
In fact, Day was nominated to the Australian Olympic team once more, in 1964 - but he stepped aside, aged 30, to let a younger skier take his place.
 
After his retirement from competitive skiing, Bill lived and worked on a Cattle Station in Talbingo, NSW. He still has fond memories of skiing with his family in Mt Selwyn up until 50 years of age. He currently lives in Wagga Wagga, NSW.