Question 115419 in Mongodb Question posted in
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How to generate random ISO date for every document in MongoDB aggregation?

I am using this code in MongoDB aggregation:

{
  date: ISODate()
}

It’s generating current date in ISO format for every document.

How can I generate random ISO date for every document?

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2

Answers


  1. 0

    The mongoDB docs on Date() / ISODate() say

    You can specify a particular date by passing an ISO-8601 date string with a year within the inclusive range 0 through 9999 to the new Date() constructor or the ISODate() function. These functions accept the following formats:

    The listed options state you can pass an integer to ISODate() in milliseconds since the UNIX Epoch (Jan 1st 1970)

    With this info you could generate a random integer between whatever starting date in milliseconds and the current date in milliseconds and pass that to the ISODate() function upon document creation giving it a random date.
    Note you’d need to generate a new random date for each document if you want them to be different.

    Here is a working example in Node.js

    function getRandomTimestamp () {
  // 1577854800 is the timestamp for 2020-01-01 00:00:00
  const minDate = 1577854800
  return Math.floor(Math.random() * (Date.now() - minDate) + minDate)
}
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  2. 0

    Try to use $rand and multiply the current UNIX timestamp with it:

    db.collection.aggregate({
  "$project": {
    "date": {
      $toDate: {
        $multiply: [
          {
            $rand: {}
          },
          {
            $subtract: [
              new Date(),
              new Date("1970-01-01")
            ]
          }
        ]
      }
    }
  }
})

    Link to playground

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