The thing there is that there is no particular time or age to start your retirement planning as people's responsibilities differs as well as their occupation.
Retirement age is not always funny especially for those who didn't make the necessary arrangements to help them survive this period. For some, they retire from work when they still got responsibility to shoulder while for a few lucky ones, it comes when they are already relieved from their responsibility such as paying for their children's school fees, feeding them, clothing then and the rest of it. Those who still got responsibilities after their retirement should take this, I mean retirement planning very seriously because the effect of it is always hard on them.
Like I said earlier, there's no specific time to start planning but from the work you do, you should know how long you are going to work there, your retirement year and then you plan accordingly.
The thing to note here is that it is always better to start early to make preparations and save up. Some people kick off with this project as soon as they got employed in their various working place.