const after_time = new Date('2021/3/12 23:00:00').getTime()
const now_time = new Date().getTime()
const hm = parseInt((now_time- after_time)/1000)//毫秒
console.log(hm) // 总共是35698毫秒
console.log('秒:',parseInt(hm%60))//35698/60=594分钟,剩余58秒
console.log('分钟:',parseInt(hm/60%60))//35698/60/60=9小时,剩余54分钟
console.log('小时:',parseInt(hm/60/60%24))//35698/60/60/24=0天,剩余9小时
console.log('天:',parseInt(hm/60/60/24))