> What's actually periodical and wraps around is only the names we give to certain lengths of time
Seasons are somewhat cyclic, to be fair. Centuries are pretty arbitrary though.
> Spiral visually implies years getting bigger or shorter which they don't.
Proper spirals imply a size change, but I suspect GP meant the shape more properly called "helix".
I get that some people want to show the periodicity of years but there's no such thing.
What's actually periodical and wraps around is only the names we give to certain lengths of time -- not time itself, be it years, centuries or what have you.