def _format_date(pdb_date):
    """Converts dates from DD-Mon-YY to YYYY-MM-DD format."""
    date=""
    year=int(pdb_date[7:])
    if year<50:
        century=2000
    else:
        century=1900
    date=str(century+year)+"-"
    all_months=['xxx','Jan','Feb','Mar','Apr','May','Jun','Jul',
    'Aug','Sep','Oct','Nov','Dec']
    month=str(all_months.index(pdb_date[3:6]))
    if len(month)==1:
        month = '0'+month
    date = date+month+'-'+pdb_date[:2]
    return date