I would like to extract the date of a Column reference (i want to pass from (21510000XXX -> 10/2015). The problem is that, the references for the years 2015 and 2016 are not the same respect to the year 2017.

It is like that:

```
DF<-c(21612000675, 21612000494, 20170100011, 21507000583, 21508000306)

```

> 
> DF
>  [1] 21612000675 21612000494 20170100011 21507000583 21508000306
> 
> 
> 

The first one is year 2016, month 12 ("216","12" number)), the third is diferent, as all 2017, so year 2017, month 01 ("2017", "01", number), the last one, as year 2015, is the same as year 2016, so year 2015 month 08 ("2015", "08", number)