const int fakeYear = 2001;
const int days = 7;

var t1 = new DateTime(fakeYear, DateTime.Now.Month, DateTime.Now.Day);
var t2 = t1.AddDays(days);

employees = ctx.Employees.Where(e => e.BirthDay >= t1 && e.BirthDay <= t2);

    const int Days = 7

    var nowMonth = DateTime.Now.Month;
    var nowDay = DateTime.Now.Day;

    return from e in ctx.Employees
        let t1 = new DateTime(e.BirthDay.Year, nowMonth, nowDay)
        let t2 = t1.AddDays(Days)
        where e.BirthDay >= t1 && e.BirthDay <= t2
        select e;

int days = 7;
var now = DateTime.Today;

var employees = from emp in ctx.Employees
                let thisYearsBirthday = emp.BirthDay.AddYears(now.[color=red]Year [/color]- emp.BirthDay.[color=red]Year[/color]) 
                let nextBirthday = (thisYearsBirthday >= now) ? thisYearsBirthday : thisYearsBirthday.AddYears(1)
                where nextBirthday >= now && nextBirthday < now.AddDays(days)
                select emp;