Sorry x posts before PFNM. In your case, I guess I'd look at how long ago it was, what your record has been since, and possibly before maternity leave, and specifically with depression, whether you have it under control. Having said that I'm not in HR and it's not my call.
For the application, I'd estimate and state that you've estimated and that if you were offered the job, you'd confirm exact dates as part of the references process. You don't exactly want to announce that you're looking for a new job.