The following is important honeybee lifecycle information which must be learnt. The numbers are days.
Queen. Worker. Drone
Hatches. 3. 3. 3
Cell sealed. 9. 9. 9
Emerges. 16. 21. 24
Variants of one day are quite common.
Roger recommends marking the queen and clipping her wings. This allows the beekeeper to have inspection intervals of 14 days.