I recover thanks to an API a json file made up like this :

```
timeline: {
  cases: {
   '5/13/21': 5902343,
   '...' : ...
  },
}

```

which then aims to constitute a chart with ChartJs

Except that in the json file the date and put in the format MM / DD / YY and I would like to change it to give DD / MM / YY