What is wrong with my code project?

I am working on a project and it gives me back an NameError, it’s supposedly not defined, but I did create my function!

""" This is a calender. It let's the user interact with the calendar"""
from time import sleep,strftime
name = "Sabrina"
calendar = { }
def welcome ():

def start_calender():
welcome (name)
start = True
while start is True:
user_choice = raw_input (" Enter A to Add, U to Update, V to View, D to Delete, X to Exit: ")
user_choice = user_choice.upper
if user_choice == "V":
if len(calender.keys()) < 1:
print "Calender empty"
else:
print calendar
elif user_choice == 'U':
elif user_choice == "A":
elif user_choice == "D":
elif user_choice == "X":
start = False
else:
print "You just put in whatever"
start = False

start_calendar()

this is the link https://www.codecademy.com/courses/learn-python/projects/calendar?action=resume_content_item

I am only new to this program myself but I can see a problem your statements and the possibility that there may be an indent or two missing!