It all depends on what suits you the best and one cannot say that what suits you is also the norm because people have different choices and there is no medical evidence to prove that waking up early is good for your health, it is the life style and your own habits that count for your well being ...

Scientists at the University of Toronto found people who preferred the evening were more prone to “social jet lag”, in which a person’s biological clock was "out of sync” with the social activities.

Here is the scientific evidence.

http://www.telegraph.co.uk/news/health/news/9327244/Why-the-early-bird-is-happier-and-healthier-in-life.html

There are advantages of waking up early for some , but it does not mean that a person who wakes up early is healthier than one who does not wake up early...There are so many around me who wake up early but because of their lifestyle are still so verry unhealthy and suffering from lifestyle diseases , so what is important is how you utilise your waking hours and not what time you wake up!

It is understood, that waking up ealy will not be the only contributing factor for a healthy life. As I said earlier, being an early riser i have enough time to do yoga, physical exercise and a plan to face the rigors of the day ahead. This is not possible for late riser.There are certain things which should be done only in the morning hours. Like I stated Doing Surya Namaskar after 10 is ridiculous and do not yield the benefits of Yoga.

That again depends on ones mindset...Yoga can be done at any time of the day and what matters is how productive your waking hours are...In fact Surya Namaskar can be done even during sun set ! It does not change the benefit in any way ..

http://www.yogicwayoflife.com/surya-namaskara-the-sun-salutation/

There is a purpose behind Surya Namaskara. The purpose is to derive the benefits of natural vitamin D from the rising Sun though Surya Namaskara can be done in the evening also but the important source of natural vitamin D will be missing. Anything can be done at any time. But there should be purpose behind what you are doing.

There is one source of Vitamin D that is free for us to use, and is one of the best sources-The Sun.

https://nishitab.wordpress.com/tag/surya-namaskar/

During my engineering days I developed the habit of studying late into night and rising up relatively late compared to others who slept early. Today also I follow the same cycle. There are advantages in both and disadvantages also. To each his style.

Vitamin D is available in plenty in our country unlike in the western countries and purpose is what one makes of it because ultimately life is what we have made out of it and what suits each individual the best ! So, medically there is no harm in following a lifestyle that is best suited to you ..

It is my Habit since my childhood to getup early in the morning. I  have seen many benefits of rising early. Hence I chose the habit of waking up early. If other ways suit an individual, he has the right to choose his own way.

I used to wake up at 5.30 when I was in high school to get milk which was distributed from an army truck since we lived in a restricted area in Bangalore...,After that I got busy with my studies and there was school and I used to take part in sports in the evening after school hours , as a result would reach home after 7..this meant I could go to bed only at 10 or even later than that.My father was a very understanding person and was particular that sleep was essential for me, so also sports and fitness, so he started going to the milk booth and made sure that I slept till 7 am , so that I remained fit and would not miss on any of the essential activities that are imperative for a healthy body and mind..