extracting date | mysql function

hi,

i know this is a php board, maybe somebody can help me with this mysql problem.

in a query generator the user can extract data from a specific date.
The confusing is it works fine until 12 days.

....WHERE acc_create BETWEEN CURDATE() - INTERVAL 12 DAY AND CURDATE() -11

This returns all users created on 31th october

but if i use
....WHERE acc_create BETWEEN CURDATE() - INTERVAL 13 DAY AND CURDATE() -12 it will mix up 30th and 31th October

and
....WHERE acc_create BETWEEN CURDATE() - INTERVAL 14 DAY AND CURDATE() -13

returns nothing although there exist values for this query

the database seems not to be corrupt
server is win2k pro english with mysql 3.2.3.51
frontend is ASP and MYODBC

greets
kristijan

... where DATE_FORMAT(acc_create,'%Y-%m-%d') = curdate() - interval 12 day;

it works