Can't figure out how to apply attributes to values in json property dictionary (System.Text.Json)

//TODO convert to DateTime
[JsonPropertyName("peace")]
[JsonConverter(typeof(UnixDateTimeConverter))]
public Dictionary<int, DateTime> Peace { get; set; }

public override DateTime Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
{
  return DateTime.UnixEpoch.AddMilliseconds(reader.GetInt64());
}