const dayjs = require('dayjs');
console.log(dayjs().format('YYYY-MM-DD HH:mm:ss')); // 2019-05-15 13:42:34
console.log(dayjs('2018/08/08').format('YYYY-MM-DD HH:mm:ss')); // 2018-08-08 00:00:00
console.log(dayjs(Date.now() - 3*24*3600*1400).format('YYYY-MM-DD HH:mm:ss')); // 2019-05-11 08:56:00
