The first day of spring is one thing, and the first spring day is another. The difference between them is sometimes as great as a month.

Van Dyke contrasts the calendar’s “official” start of spring with the lived, sensory arrival of spring weather. The line points to the gap between abstract definitions and embodied experience: an equinox can be marked precisely, yet the first truly springlike day—soft air, thawed ground, returning birds—may come much earlier or later. By saying the difference can be “as great as a month,” he underscores how nature resists human timetables and how seasonal change is felt locally rather than universally. The remark also carries a gentle reminder to attend to reality over labels: what matters is not the date we declare, but the moment the world actually turns.