You can find plenty of examples of both morning and evening people who are happy, healthy and productive, so it's important to find out what suits you and do it if you can. However, there is evidence that 'extreme owls', ie people who really hate getting up in the morning and stay up very late at night, may have health problems and be less happy than those whose body clocks are more in tune with the daylight. This is probably partly because we do need some air and sun to keep us healthy, and if you're someone who doesn't get going until lunchtime you may not get enough of those. Also, the 'night owl' lifestyle often goes with not getting enough sleep, regular meals etc. For these and other reasons, health experts do recommend that if you are more of a night person you may be advised to try and alter your habits a bit, in favour of more daylight etc.