Nowadays, commercial strains of laying hens lay the majority of their eggs (about 90%) during the morning (Leeson and Summers, 1978). Also, shell is deposited around the albumen when the egg remains in the shell gland. The period of shell deposition coincides mainly in the afternoon and evening. As a result of these processes, hens my have higher calcium (Ca) requirement during the afternoon and in evening. The higher phosphorus (P) requirement in the morning is needed to replace the bone minerals which have been reabsorbed during the previous night when shell formation occurred. (Keshavarz, 1998). Regarding these facts, it has been shown that reducing dietary P during the afternoon and evening had a beneficial effect on shell quality (Roland and Harms, 1976). Hence, we investigated if it would be possible to improve laying performance and egg quality when hens received diets with adequate levels of P only in the morning and Ca only in the afternoon and evening.