Option set with start date and end date field

Hi this is Bharath, I have 1 option set with q1,q2,q3,q4 options.i have start date and end date fields.i have to populate start date and end date fields based on q1,q2,q3,q4  using javascript.

example q1 starts at 01-06-2018 and ends at 31-08-2018.like this i want to populate date fields.

Thanks,

Bharath.