wochentage = ["SON", "MON", "DIN", "MIT", "DON", "FR", "SAM"]
monaten = [None, 
"JAN", "FEB", "MAR", "APL", 
"MAI", "JUN", "JUL", "AUG", 
"SEP", "OKT", "NOV", "DEZ"]


x = monaten[1::4]  # Monaten JAN, MAI, SEP
print(x)
y = monaten[1:8:2] # JAN, MAR, MAI, JUN
print(y)
z = monaten[1:8]
print(z)           # JAN, FEB ... , JUL
a = monaten[-1:1:-2]
print(a)