I kind of like this one, which doesn't deal with indices.  Maybe?

```python
def create_date(strdate):
    return datetime.datetime.strptime(strdate, '%Y-%m-%d').date()

def parse_date(strdates):
    dates = strdates.split(",")
    if len(dates) == 2:
        begin, end = map(create_date, dates)
    elif len(dates) == 1:
        begin, end = map(create_date, ['2005-12-19'] + dates)
    else:
        raise ValueError('You must specify either one or two dates only.')
    return {'begin' : begin, 'end' : end}
```