How to get all dates in the last X months

I want to get all dates in the last three months, so I did the following:

protected void BindPermissions(int empNum)
        {
            var permPeriod = new Dictionary<int, int>();
            permPeriod.Add(DateTime.Now.Year, DateTime.Now.Month);
            permPeriod.Add(DateTime.Now.AddMonths(-1).Year, (DateTime.Now.AddMonths(-1).Month));
            permPeriod.Add(DateTime.Now.AddMonths(-2).Year, (DateTime.Now.AddMonths(-2).Month));
            var dt = payload_object.AttendancePermissionBO.permissionList
                .Where(x => x.empNum == empNum
                && ((x.permDate.Year == permPeriod.Keys.ElementAtOrDefault(0) && x.permDate.Month == permPeriod.Values.ElementAtOrDefault(0)) ||
                (x.permDate.Year == permPeriod.Keys.ElementAtOrDefault(1) && x.permDate.Month == permPeriod.Values.ElementAtOrDefault(1)) ||
                (x.permDate.Year == permPeriod.Keys.ElementAtOrDefault(2) && x.permDate.Month == permPeriod.Values.ElementAtOrDefault(2)))).ToList().OrderBy(x => x.permDate);
            GV_PermissionHistory.DataSource = dt;
            GV_PermissionHistory.DataBind();
        }

Is there a better way to do that or this method suits what i need?

>Solution :

1. Get the date (boundary) three months ago from today.

DateTime threeMonthsAgoDate = DateTime.Now.AddMonths(-3);

2. Filter the data for permDate that after (inclusive) the date from 3 months ago.

var dt = payload_object.AttendancePermissionBO.permissionList
    .Where(x => x.empNum == empNum
        && x.permDate >= threeMonthsAgoDate.Date)
    .OrderBy(x => x.permDate)
    .ToList();