membership packages-bug?

Hi
new membership packages dont start from expired date . its start from the Present date
this is a bug

for example
i have 3 membership packages 1 month, 3 month,6 month
when a user bought a membership packages for 3 months lets say the date 1/3
the expired date will be 1/6 so far its good.
after a mount the user want to buy more 6 months(not to renew the 3 months) so the expired date should be added to the expire date
its 1/7 + 6 months = 1/12
bot no , its take the present date(1/4) + 6 months = 1/10
this is a bug
could it be fixed?
thanks
ben