d1 = c1 = x1 is the today daytime period of c2 = x2 at location n3 = x3.
Usage rules are exactly analogous to those of "cabycte". This is the diurnal period which ranges from morning/sunrise until dusk/sunset for the calendrical or circadian rhythm (or similar) full day which the speaker, via x2 and "x_3$, considers to be 'today'.