如何计算到下个月的第二天？

Question

For unit testing I need the duration, how long it is until the next second day of the month. Example: Today => 20. Jan 2018 Next second day of month => 2. Feb 2018

What I need: Time in milliseconds until 2. Feb 2018

Answer 1

You could calculate the time difference until the end of the month and then add an additional 2 days worth of milliseconds to the end of your calculated time ( 2*((60000*60)*24) ). I've provided a generalized approach which allows you to perform this calculation for the n th day in a given month:

 const get_next_nth = n => today => today.getDate() < n-1 ? (n-(today.getDate()+1))*60000*60*24 : (new Date(today.getFullYear(), today.getMonth() + 1, 0) - today) + n*((60000*60)*24); const get_next_second = get_next_nth(2); const res = get_next_second(new Date()); console.log(res); // m/s until next 2nd date console.log(new Date(new Date().getTime() + res).toDateString()); // string version of next 2nd date 

Answer 2

You can solve this problem using moment.js with the flowing process.

1. First find the second month.

let nextMonth = moment(new Date()).add(1, "M").toDate(); ==> Wed Oct 02 2019 18:24:31 GMT+0600

2. Find start of the month.

let startOfMonth = moment(nextMonth).startOf("month").toDate(); ==> Tue Oct 01 2019 00:00:00 GMT+0600

3. Find the second day of the month.

let secondDay = moment(startOfMonth).add(1, "d").toDate(); ==> Wed Oct 02 2019 00:00:00 GMT+0600