Vaguely sinusoidal (high in summer, low in winter, continuing to the next year). The actual siusoidal ribbon is a calendar of a kind I've seen many times. This

Vaguely sinusoidal (high in summer, low in winter, continuing to the next year). The actual siusoidal ribbon is a calendar of a kind I've seen many times. This is kind of how I visualize future dates sometimes, I see them on this calendar.