\\SO answer ...

README.md

How to access a json key when it is a number?

here is my answer :

https://stackoverflow.com/questions/67009657/how-to-access-a-json-key-when-it-is-a-number/67010545#67010545

json_number.js

let json=[
{
   "track": "Virtual 1",
      "data": {
         "20210310": [
         {
            "start": "8:20 a.m.",
            "end": "",
            "company": "Otonomo",
            "ticker": "OTON"
         } ]
      }

}];

((dataStr) => { dataStr.forEach( function(n, i) {
  console.log(i+':',n);
  console.log(Object.keys(n.data));
  Object.keys(n.data).forEach(
   k => {
   let day = k.replace(/(....)(..)(..)/,`$1-$2-$3`);
   let time = n.data[k][0].start.replace(' a.m.','')
   let date = new Date(`${day} ${time}`);
     console.dir(date.toGMTString())
     console.dir(n.data[k]) 
     // some code here using n.data[k];
     // like createTableCells(tab1, n.data[k]);
     console.info(`${k}: ${n.data[k][0].ticker}; start: ${date}...`);
   });
   
  } )
})(json);