1. badly indented monthDict content (and not only because the four spaces in place of a tab; ending brace should occur in a separate line, if you format like this)

2. trailing whitespaces in many lines (including, but not limited to, empty lines with whitespaces)

3. too long lines

4. bad command line arguments processing (should be optparse or argparse)

5. bad operation separation (addEvent() being the first example -- too complex, too many things being done on the same level)

6. string formatting done badly (you should use printf-like formatting instead of string concatenation)

7. code duplication (getEventsToday() vs. getEventsTomorrow())