Average difference between multiple dates in column

[PompeuPD]

Hi,

In this query I have two separate tables. One with baby cows that have been born, and the second with the mothers.

In the first one I have the following columns

Baby cow ID

Mothers ID code 

Date of birth

In the second I have the following column

Mothers ID code

The problem is that the same mother can give birth multiple times. So in the first table I sometimes have the same Mothers ID code with different birth dates

I want to be able to calculate the average time difference, that a given cow gives birth so that i end up with a table with these columns:

Mothers ID code

Month Average between Births (For example: 12.3 months)

I merged the two tables but i ended up with duplicates Mothers ID code (as expected), and i dont know where to go from there.

Table after merge:

Mothers ID code         Date of birth

1001                            10/2/2015

1001                            11/2/2016

1001                              7/3/2017

1002                            10/4/2017

1003                            7/10/2016

1003                              8/9/2017

...

The result I want:

Mothers ID code      Month Average between births

Hope that someone can help me