Weeks elapsed to Months elapsed conversion

Hi all,
I have a simple question (tried googling but found no answers). How do I 
convert weeks elapsed into months elapsed?
I have data that contains duration in weeks (without any other date 
values such as year and so on) for example a week value of 14 and I 
would like to convert the 14 weeks to 3 months (some lose of accuracy 
expected).
Expected tests may be:
14 weeks yields 3 months.
1 weeks yields 0 months.

Is there such a function. The rudimentary solution (may reduce lose of 
accuracy) am thinking of is to add the weeks to the value returned by 
clock_timestamp() then subtract clock_timestamp() from it. The question 
now is how to convert the returned value to months elapsed as opposed to 
days elapsed.

Allan.