Postman - How set up one specific “value” for all pairs “key”=“value” in the body before sending Request

I’d like to ask if I can set up one specific “value” for all pairs “key”=“value” in the body before sending Request. My request body:

{
“shop_status”: “GOLD”,
“city”: “LA”,
“name”: “Beard Shop”
“offers”: [
{
“created_at”: “2020-04-15T15:14:03.548282Z”,
“offer_id”: “oof010329182”,
“amount”: “320”,
},
{
“created_at”: “2020-04-02T15:14:03.548282Z”,
“offer_id”: “oof010329183”,
“amount”: “180”,
},
{
“created_at”: “2020-04-01T15:14:03.548282Z”,
“offer_id”: “oof010329184”,
“amount”: “750”,
}
}

I need to set up the one date for all “created_at” keys. How can I do it?