Query Criteria Where Date = Max Date - 3 months

I currently have quarterly data for employees where PerEndDt represents the end date for each quarter

The following Sql queries the current quarter. How can I modify it to return the prior quarter?
SELECT qEmplByMth.Clock, qEmplByMth.EmployeeName, qEmplByMth.Program, qEmplByMth.PerEndDt
FROM qEmplByMth
WHERE PerEndDt IN(SELECT MAX(PerEndDt ) FROM qEmplByMth)
ORDER BY qEmplByMth.EmployeeName, qEmplByMth.PerEndDt;