Vue2のテンプレート内部で、momentが使えなかった、dataに渡してあげると解決。

import moment from 'moment';
moment.locale('ja');

new Vue({
    el: '#myApp',
    data: {
        moment: moment
    },
.
.
.

出ていたmomentが参照できないよとエラー

app.js:43920 [Vue warn]: Property or method "moment" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property.

参考 :
https://stackoverflow.com/questions/58342090/typeerror-vm-moment-is-not-a-function-in-vuejs