how to much time it will take to create a small game in unity by one person

Answer 1

If its a small indie game it might take about 1 week for a short prototype.
About 1 month for completing it.

In case if a big official game it might take about 1 month for the complete prototype.
And may take from 3months to even 2years, to complete it.

These calculations maybe wrong, because its JUST an estimation.

The time actually depends on how, what, when you make.

Answer 2

If it's a snake game, maybe a day.