iCalWeekGenerator is a commandline based tool that could be used to generate recurring weekly events with an icon in iCal format. The goal is to have a small icon on every Monday (or other day) holding the week number. I use this to mark weeks in the academic calendar.

iCalWeekGenerator.py

import argparse
from datetime import date
from datetime import datetime
from datetime import timedelta

"""
    TODO: Add timezone support
"""

# Global Variables
DAYS_PER_WEEK = 7
ICON_URL = 'X-GOOGLE-CALENDAR-CONTENT-ICON:http://www-scf.usc.edu/~alghanmi/images/week{}.png'
ICON_ABOUT_URL = 'X-GOOGLE-CALENDAR-CONTENT-URL:http://www-scf.usc.edu/~alghanmi/calendar/about.html'

def getDate(datestr):
    """ Given a date in %Y-%m-%d, return the date object  """
    return datetime.strptime(datestr, '%Y-%m-%d').date()

def getvCalendarHeader(calName):
    """ vCalendar Header """
    if calName == None:
        calName = ''
    
    return  ['BEGIN:VCALENDAR',
            'VERSION:2.0',
            'X-WR-CALNAME:{}'.format(calName),
            'X-WR-TIMEZONE:US/Pacific',
            'CALSCALE:GREGORIAN']

def getvCalendarFooter():
    """ vCalendar Header """
    return ['END:VCALENDAR']

def getvEvent(startDate, title, weekNo, icon):
    """ vEvent Entry into Calendar """
    eventStartString = date.strftime(startDate, '%Y%m%d')
    eventEndSting = date.strftime(startDate + timedelta(days=1), '%Y%m%d')
    
    if title == None:
        title = 'Week {}'.format(weekNo)
    
    vevent = []
    vevent.append('BEGIN:VEVENT')
    vevent.append('DTSTART;VALUE=DATE:{}'.format(eventStartString))
    vevent.append('DTEND;VALUE=DATE:{}'.format(eventEndSting))
    vevent.append('SUMMARY:{}'.format(title))
    if(icon == True):
        vevent.append('X-GOOGLE-CALENDAR-CONTENT-TITLE:{}'.format(title))
        vevent.append(ICON_URL.format(weekNo))
        vevent.append(ICON_ABOUT_URL)
        vevent.append('X-GOOGLE-CALENDAR-CONTENT-TYPE:text/html')
        vevent.append('X-GOOGLE-CALENDAR-CONTENT-WIDTH:205')
        vevent.append('X-GOOGLE-CALENDAR-CONTENT-HEIGHT:45')
    
    vevent.append('END:VEVENT')
    
    return vevent

# Argument Parser
parser = argparse.ArgumentParser()
# Required arguments
parser.add_argument('start', help='Start date of first week in yyyy-m-d format', type=getDate)
parser.add_argument('weeks', help='number of weeks to generate', type=int)
# Optional Arguments
parser.add_argument('-n', '--name', help='Calendar name', type=str, dest='name')
parser.add_argument('-t', '--event-title', help='Title for weekly event to prepend week number', type=str, dest='title')
parser.add_argument('-f', '--first-week-day', help='The first day of the week', choices=['Sat', 'Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri'], default='Mon', dest='weekday')
parser.add_argument('-e', '--events-only', help='Only output events without calendar headers', action='store_true', dest='vevent')
parser.add_argument('-s', '--start-number', help='The number of the first week', type=int, default=1, dest='weekNo')
parser.add_argument('-i', '--icons', help='Add icons to events', action='store_true', dest='icons')
# Parse Arguments
args = parser.parse_args()

cal = []
# Print vCal Header
if args.vevent == False:
    cal.append(getvCalendarHeader(args.name))

weeks = args.weekNo
sdate = args.start

for i in range(0, args.weeks):
    weekTitle = args.title + " " + str(weeks)
    cal.append(getvEvent(sdate, weekTitle, weeks, args.icons))
    sdate += timedelta(days=7)
    weeks += 1

if args.vevent == False:
    cal.append(getvCalendarFooter())

for c in cal[:]:
    for line in c[:]:
        print line
    print ''

For usage instructions:

python iCalWeekGenerator.py --help

Example to generate an iCal calendar for a 17-week semester starting on 2013-01-14 with weeks starting on a Monday:

python iCalWeekGenerator.py 2013-01-14 17 --name "Spring 2013 Semester" -t "20131 Week" --first-week-day Mon --icon

This command does the same, but without generating the vCalendar code. This is used to insert into an existing calendar:

python iCalWeekGenerator.py 2013-01-14 17 --name "Spring 2013 Semester" -t "20131 Week" --first-week-day Mon --icon --events-only