Get date value from header

Question

I'm trying to use Google Sheets as a JSON backend. The JSON output is here:

           "gsx$company": {  //all is ok
                "$t": "Company name"
            },
            "gsx$_clrrx": {  //might be 12.02.16
                "$t": "132"
            },
            "gsx$_cyevm": {  //might be 17.02.16
                "$t": "142"
            },
            "gsx$_cztg3": {  //...
                "$t": "155"
            }

In table header I have a date value. But I can't get the right field name from header. It always returns random name, like this _cztg3.

How can I get the date from header?

Table example