Development does not unfold according to uniform external time alone. Biological development is organised through processes whose timing, duration, sequence, and coordination can make a material difference to developmental trajectories and outcomes.
Growth, differentiation, regulation, signalling, metabolic activity, ecological interaction, and other developmentally relevant processes may occur at different rates and over different temporal extents. Some developmental transitions are rapid, while others involve prolonged reorganisation. Their biological significance can depend not simply on how much clock time passes, but on when processes occur, how long they persist, and how they are temporally related to other processes.
APS therefore distinguishes chronological duration from developmental temporality. Developmental temporality concerns biologically relevant relations of timing, sequence, duration, recurrence, and historical context within developmental processes. Which temporal relations are explanatorily important must be established for the biological case concerned.
Such temporal organisation may contribute to developmental continuity or persistence, but neither continuity nor successful viability maintenance defines developmental time. Temporal relations can also be associated with redirected development, developmental arrest, dysfunction, or other outcomes.
Key point: developmental time concerns biologically relevant temporal organisation rather than uniform external clock duration alone.