Depending on your browser or your device, the date picker will vary.  For mobile devices, the loan form currently tries to prompt the native date picker of the device. 
There are variances between iOS and Android that might be confusing.  For the iPhone, the date picker is pretty straightforward and it's pretty easy to change the year.  However, on an Android it's not as obvious.  The trick is to tape on the year itself, which pops up a rolling list of other years to choose from.  See the illustration below (the spot to tap is circled).

Selecting a birth year - sample of the Android date picker