Well one, if they're sleeping all night they just might not be tired during the day. But you can also think of this.... is there a lot of noise during the day at your house? Are you up and busy and cleaning the house or have the tv up loud maybe, or something like that? Do you try to have your child sleep in the same place during the day for naps as you do at night? Do you put your child in a swing or bouncy seat during the day but their actual crib at night? Do you play a mobile for them above their crib to get them to go to sleep at night but not during the day? Many different things could be the issue or just one of them. However your baby is sleeping at night, whatever they need to help them fall asleep, try the same things during the day. If you already are doing the same things, then maybe you need to try something different. Try rocking the baby until they fall asleep and then put them to bed. Try a swing or bouncy seat to get them to fall asleep. Keep trying different things until you find what works. If nothing is helping and you think something might be wrong, call up your doctor and ask. It's better to be safe than sorry.