Example.cs

using System.Collections;
using Kogane;
using UnityEngine;
using UnityEngine.Networking;

public class Example : MonoBehaviour
{
    private IEnumerator Start()
    {
        const string url =
            "https://www.timeapi.io/api/Time/current/zone?timeZone=Asia/Tokyo";

        var request = UnityWebRequest.Get( url );

        yield return request.SendWebRequest();

        var json        = request.downloadHandler.text;
        var jsonTimeAPI = JsonUtility.FromJson<JsonTimeAPI>( json );

        Debug.Log( jsonTimeAPI );
    }
}

JsonTimeAPI.cs

// ReSharper disable InconsistentNaming

using System;
using UnityEngine;

namespace Kogane
{
    [Serializable]
    public struct JsonTimeAPI
    {
        [SerializeField] private int    year;
        [SerializeField] private int    month;
        [SerializeField] private int    day;
        [SerializeField] private int    hour;
        [SerializeField] private int    minute;
        [SerializeField] private int    seconds;
        [SerializeField] private int    milliSeconds;
        [SerializeField] private string dateTime;
        [SerializeField] private string date;
        [SerializeField] private string time;
        [SerializeField] private string timeZone;
        [SerializeField] private string dayOfWeek;
        [SerializeField] private bool   dstActive;

        public int    Year         => year;
        public int    Month        => month;
        public int    Day          => day;
        public int    Hour         => hour;
        public int    Minute       => minute;
        public int    Seconds      => seconds;
        public int    MilliSeconds => milliSeconds;
        public string DateTime     => dateTime;
        public string Date         => date;
        public string Time         => time;
        public string TimeZone     => timeZone;
        public string DayOfWeek    => dayOfWeek;
        public bool   DstActive    => dstActive;

        public override string ToString()
        {
            return JsonUtility.ToJson( this, true );
        }
    }
}