Joomla 2.5.17
Cb 1.9.1

I create a date field, let's call it cb_birthday and set it for registration.
In the registration page in the front-end, if I start fill the cb_birthday field from the day drop down list, it shows only the values for the current month.

I.E. if it is february, and I'll go to the registration page and start to fill in the day value without changing the month first (blank), i'll get only values from 1 to 28.

It may seems to You like a non-existent issue, but I actually receive emails every now and then from users who tries to registers and cannot find their day number...

Is there any workaround?
Thanks in advance for any help You can give me.