I've a column with different types of date such as:

```
2\06\1998
21.11.1998  
18-02-2001
03/05/1999 
20 july 1999

```

I only want the year.

I tried different type of regex such as:

```
def get_date(date):
        number= re.findall('\[0-9]\-{0,1}\\{0,1}\/{0,1}\[0-9]\-{0,1}\\{0,1}\/{0,1}\[0-9]', date)
        return number[6:]

```

but I can't extract the year.
what's the most suitable regex for this case? 
it's not a problem to do two types of regex, one for the format dd/mm/yyyy and one for the date with month in letter.