def dob():
    if not os.path.exists('analytics'):
        os.mkdir('analytics')
    if os.path.exists('analytics/dob'):
        shutil.rmtree('analytics/dob')
    with open('studentinfo_cs384.csv', newline='') as csvfile:
        reader = csv.DictReader(csvfile)
        if not os.path.exists('analytics/dob'):
            os.mkdir('analytics/dob')
        for row in reader:
            l = list(row.values())
            head = list(row.keys())
            x = str(re.sub(r"\D","-",row['dob']))
            yr = int(x.split('-')[-1])
            k = int(yr)%10
            if k>4:
                name = 'bday_' + str(yr - k + 5) + '_' + str(yr - k + 9)
            else:
                name = 'bday_' + str(yr - k ) + '_' + str(yr - k + 4)
            if yr > 2014:
                name = 'bday_2015_2020'
            with open('analytics/dob/'+name+ '.csv', mode = 'a') as f:
                    f_write = csv.writer(f, delimiter=',',lineterminator='\r')
                    if os.path.getsize('analytics/dob/'+name+ '.csv')==0:
                        f_write.writerow(head) 
                    f_write.writerow(l)
            f.close()