Each band, from under a day through to over ten years, shows the share of supply last moved in that window. Bands mature upward over time if coins sit still, and collapse downward when old supply moves.
Read as a picture of conviction and distribution. Thickening long-duration bands during a drawdown mean coins are settling into hands that are not selling; rapid growth in the youngest bands during a rally means supply is changing hands quickly, which historically accompanies late-cycle behaviour.
It shares every limitation of address-based analysis. Custodial holdings appear as one enormous wallet regardless of how many customers sit behind it, lost coins age forever and permanently inflate the oldest band, and exchange migrations distort the young bands.
Related: dormancy, coin-days-destroyed, supply-in-profit, realized-cap