I want to create a date selection form with Vue.js.

https://www.kabanoki.net/3905/
I created this site as a reference, but an error occurs and it is no longer displayed.

Error message

[Vue warn]: Unknown custom element:<v-date-picker>-did you register the component correctly? For recursive components, make sure to provide the "name" option.
found in
--->at app/javascript/packs/components/about.vue
       <Root>

Applicable source code

<template>
  <v-date-picker: mode = "mode"
               : formats = "formats"
               v-model = "selectedDate"></v-date-picker>
</template>
<script>
import Vue from 'vue';
import VCalendar from 'v-calendar';
Vue.use (VCalendar);
export default {
  data: function () {
    return {
    mode: 'single',
    formats: {
        input: ['YYYY-MM-DD'],
    },
    selectedDate: null,
    }
  }
}

</script>

https://www.kabanoki.net/3890/
V-calendar has been installed with npm referring to this site.
I don't know what caused it ...