该模块导入错误

尝试导入Date模块并在简单的Elm文件中使用它时，出现以下错误：

-- UNKNOWN IMPORT ---------------------------- app/javascript/CountdownTimer.elm

The CountdownTimer module has a bad import:

    import Date

I cannot find that module! Is there a typo in the module name?

The "source-directories" field of your elm.json tells me to only look in the src
directory, but it is not there. Maybe it is in a package that is not installed
yet?

CountdownTimer是文件和模块的名称，取自此处，似乎工作正常，但不适用于我。

我正在使用Elm 0.19.0和Rails 6.0.0beta1，这似乎不是一个约束，因为如果我在任何地方输入Elm REPL，并尝试导入日期，我都会遇到相同的错误：

> import Date
-- UNKNOWN IMPORT ---------------------------------------------------------- elm

The Elm_Repl module has a bad import:

    import Date

I cannot find that module! Is there a typo in the module name?

When creating a package, all modules must live in the src/ directory.

我的elm.json文件如下所示：

{
    "type": "application",
    "source-directories": [
        "src"
    ],
    "elm-version": "0.19.0",
    "dependencies": {
        "direct": {
            "elm/browser": "1.0.1",
            "elm/core": "1.0.2",
            "elm/html": "1.0.0",
            "elm/time": "1.0.0",
            "elm/json": "1.1.2",
            "elm/url": "1.0.0",
            "elm/virtual-dom": "1.0.2"
        },
        "indirect": {
        }
    },
    "test-dependencies": {
        "direct": {},
        "indirect": {}
    }
}