Convert US date to European date - test 3 fails

Question

I see a lot of postings for this question, I like your regex approach, everyone! Please help me fix my solution, I don't know why the third hidden case fails:

https://code.sololearn.com/cn0Mv5cKlZGF/?ref=app

Answer 1

It gives some weird outputs if day or month is a single digit.
For example,
7/26/2019 returns 6//7//019

Answer 2

Simba, thank you for pointing that out. I didn't think about single digit months and/or days