Ever since the late 1970s, I have used the nordic skier's training year, which begins on May 1st. Back then I was a nordic racer, and partly because it also worked for me as a climber ... ice climbing ended in March, and rock climbing not really heating up until May.
As per the last week of the old training year, it was another transitional week when I logged almost 16 hours, with 165k (biking, running, ergometer). It was also the first week since November with no skiing, and under 4000' vertical.