Question 179209 in Javascript Question posted in
A very good W3school tutorial can be found here.

“How can I get a date month ago from a constant start date in Javascript?”

I need to render a subscription date range on a page like this:

31 May 2023 — 30 June 2023

When user subscribes then backend sends a subscription start date (it never changes and always the same). For example if user subscribed on 31 May 2023 then the start date will be:

const startDate = "2023-05-31T10:16:14+00:00"

Then there’re nextDates when a new credits will be added to user account

  const nextDate = "2023-06-30T10:16:20.404358+00:00",
  const nextDate1 = "2023-07-31T10:16:20.404358+00:00",
  const nextDate2 = "2023-08-31T10:16:20.404358+00:00",

So my question is how can I get the start date for each nextDate?
The output should be like this:

const startDate = "2023-05-31T10:16:14+00:00"
const nextDate = "2023-06-30T10:16:20.404358+00:00" // startDate should be 31 May 2023
const nextDate1 = "2023-07-31T10:16:20.404358+00:00" // startDate should be 30 June 2023

I tried this but the output is incorrect:

const getPreviousInterval = (nextDate, months) => {
  const date = new Date(nextDate);
  const dateMonthsAgoUnix = date.setMonth(date.getMonth() - months);

  return new Date(dateMonthsAgoUnix);
};

getPreviousInterval("2023-06-30T10:16:20.404358+00:00", 1);
// incorrect output is 2023-05-30T10:16:20.404Z
// correct output is 2023-05-31T10:16:14+00:00
Tags:

4

Answers


  1. 0 
    const date = new Date(Date.now());
const oneMonthAgo = new Date(date.setMonth(date.getMonth() + 1));

console.log(oneMonthAgo);
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  2. 0 
    // gets today's date
const date = new Date();

// gets the date from one month ago
const oneMonthAgo = new Date();
oneMonthAgo.setMonth(oneMonthAgo.getMonth() - 1);

console.log("Today's date is " + date.toLocaleDateString());
console.log("Three months ago, the date was " + oneMonthAgo.toLocaleDateString());
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  3. 0

    Seems like you want the last day of the previous calendar month rather than something "one month ago". See details of setDate(0) here.

    const getPreviousInterval = (nextDate, months) => {
  const date = new Date(nextDate);
  date.setMonth(date.getMonth() - months + 1);
  date.setDate(0); // setDate(0) gives the last day of the previous month
  return date;
};

console.log(getPreviousInterval("2023-06-30T10:16:20.404358+00:00", 1));

console.log(getPreviousInterval("2023-06-30T10:16:20.404358+00:00", 4));

console.log(getPreviousInterval("2023-06-30T10:16:20.404358+00:00", 40));
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  4. 0

    You can try to build a list of future dates by adding a month to the date and then one day in milliseconds each time.

    You can then use the Intl.DateTimeFormat class to format the date in British format.

    const dateFormatter = new Intl.DateTimeFormat('en-GB',  // UK date format
  { day: '2-digit', month: 'short', year: 'numeric' }); // DD MMM YYYY

const formatDateRange = (fromDate, toDate) =>
  `${dateFormatter.format(fromDate)} — ${dateFormatter.format(toDate)}`;

const computeFutureMonths = (startDate, months) => {
  const results = [], currDate = new Date(startDate.getTime());
  for (let i = 0; i < months; i++) {
    currDate.setMonth(currDate.getMonth() + 1);
    results.push(new Date(currDate.getTime() - 8.64e7)); // Subtract 1 day in ms
  }
  return results;
};

const startDate = new Date('2023-05-31T10:16:14+00:00');
const nextThreeMonths = computeFutureMonths(startDate, 3);

nextThreeMonths.forEach(date => {
  console.log(date.toISOString());
});

// 31 May 2023 — 30 Jun 2023
console.log(formatDateRange(startDate, nextThreeMonths[0]));
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