This is a question that would have literally have taken two seconds to look up on google but the answer is 1.88 years.
As we know that as per Newton's II law we have

here we will have
= change in momentum
= time interval in which momentum is changed
now in order to have least injury during jumping we need to have least force on the jumper
so in order to have least force we can say that the momentum must have to change in maximum time so that amount of force must be least
So we need to increase the time in which momentum of the system is changed
For a body moving at a uniform velocity you can calculate the speed by dividing the distance traveled by the amount of time it took, for example one mile in 1/2 hour would give you 2 miles per hour. If the velocity is non-uniform all you can say is what the average speed is.
HOPE IT HELPS YOU
the SL unit of acceleration is the meter per second squared