Input JSON lost when doing a date concat

[mordfustang00]

Good Day. I would like to seek for assistance to achieve the following scenario:

Input would be:

{
"CarStat": {
"mileage": {
"value": 1000
}
},
"header": {
"Date": "Fri, 29 Mar 2024 17:50:26 GMT",
"Offset": "-7"
}
}

Output should be:

{
"CarStat" : {
"mileage" : {
"value" : 1000
}
},
"header" : {
"Date" : "20240329175026.000",
"Offset" : "-7",
"year" : "2024",
"month" : "03",
"day" : "29",
"timeHH" : "17",
"timeMM" : "50",
"timeSS" : "26",
"sss" : ".000"
}
}

But output looks like this:

{
"CarStat" : {
"mileage" : {
"value" : 1000
}
},
"header" : {
"Date" : "2024Mar29175026.000",
"Offset" : "-7",
"year" : "2024",
"month" : "Mar",
"day" : "29",
"timeHH" : "17",
"timeMM" : "50",
"timeSS" : "26",
"sss" : ".000"
}
}

This is the current spec:

[
{
"operation": "modify-overwrite-beta",
"spec": {
"header": {
"year": "=substring(@(1,Date), 12, 16)",
"month": "=substring(@(1,Date), 8, 11)",
"day": "=substring(@(1,Date), 5, 7)",
"timeHH": "=substring(@(1,Date), 17, 19)",
"timeMM": "=substring(@(1,Date), 20, 22)",
"timeSS": "=substring(@(1,Date), 23, 25)",
"sss": ".000"
}
}
},

{
"operation": "shift",
"spec": {
"*": "&",
"month": {
"Mar": {
"#3": "month"
}
}
}
},
{
"operation": "modify-overwrite-beta",
"spec": {
"header": {
"month": "=substring(@(1,Date), 4, 1)",
"Date": "=concat(@(1,year),@(1,month),@(1,day),@(1,timeHH),@(1,timeMM),@(1,timeSS),@(1,sss))"
}
}
}
]

Many Thanks.