JED (1.6.0+) - Custom day cycle for the Overworld

{
    "dimensions": [
        {
            "dim": 0,
            "override": true,
            "dimensiontype": {
                "id": 0,
                "name": "overworld",
                "suffix": "",
                "keeploaded": true,
                "worldprovider": "WorldProviderSurfaceJED",
                "require_exact_match": true
            },
            "jed": {
                "CustomDayCycle": true,
                "DayLength": 48000,
                "NightLength": 48000
            }
        }
    ]
}