Try the below.
[{"id":"50b1a1d1.ed892","type":"file","z":"4a8e69ed.f81b98","name":"Add Device file location","filename":"","appendNewline":true,"createDir":true,"overwriteFile":"true","encoding":"none","x":550,"y":80,"wires":[["bda46195.b38b1"]]},{"id":"c6679eea.8efd","type":"function","z":"4a8e69ed.f81b98","name":"Data Capture","func":"var d = new Date();\nvar t = d.getTime();\nvar n = d.getTimezoneOffset();\npayload={\"date/time\": d,\"Time Zone Diffrence in minutes\": n,\"IP\": msg.ip,\"Bacnet\": msg.Bacnet, \"Function\": msg.Function, \"type\": msg.ObjectID,\"App Tag\": msg.Apptag, \"Property ID\": msg.PropertyID, \"Write Value\": msg.Wvalue, \"payload\":msg.payload};\nmsg.payload=payload;\nreturn msg;","outputs":1,"noerr":0,"x":190,"y":80,"wires":[["eafe30f8.658b"]]},{"id":"eafe30f8.658b","type":"json","z":"4a8e69ed.f81b98","name":"","property":"payload","action":"","pretty":false,"x":350,"y":80,"wires":[["50b1a1d1.ed892"]]},{"id":"bda46195.b38b1","type":"debug","z":"4a8e69ed.f81b98","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":750,"y":80,"wires":[]}]