Question 168714 in Mongodb Question posted in
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How can Node.js/JS convert DB dates to HTML date inputs w/o weird behaviour?

Hope and appreciate to get some explanation for the following

The problem is about dates, and I know I could use a package like moments, though, in this situation I don’t need to use dates that much. I also know that day and month obtained from respective Date get functions return a value which is one less then the actual corresponding value.

So, I have a form that saves data to a database and as for displaying saved data I need to convert dates to the format yyyy-mm-dd and for that I use a small function and the approach of separating date parts and rejoin them in proper order for the date picker.

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The function used to format the dates (sorry for all the logs)

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This function is called twice for each record, because there are two dates per record, and the console output is the following:

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// the code for the function

export function dateToPug(dateIso) {

    console.log('ndate string from db' , dateIso, 'n')
    
    const date = new Date(dateIso)
    
    console.log('toDateString',date.toDateString(), 'n')

    console.log('date string converted to date', date.toISOString(), 'n')
    
    const day = (date.getDate())// + 1)
    
    console.log('day extracted from date', day, 'n')
    
    // day < 10 ? day =`0${date.getDate()}` : ''
    
    const month = (date.getMonth())// + 1) 

    console.log('month extracted from date', month, 'n')

    // month < 10 ? `0${date.getMonth()}` : ''

    const year = date.getFullYear()

    console.log(`${year}-${month}-${day}`, 'n')

    return `${year}-${month}-${day}`

}

// the outupt

date string from db **1900**-**10**-**10**T00:00:00.000Z       // first date from the database record

toDateString Tue **Oct** **09** 1900        // converted to date string changes the day but not the month

date string converted to date **1900-10-10**T00:00:00.000Z    // date in iso format

day extracted from date **9**          // got day -1 as expected

month extracted from date **9**        // got month -1 as expected

**1900-9-9**     // date in format for the form input date (with trimmings that will have to be removed)


date string from db **1950**-**10**-**10**T00:00:00.000Z     // second date from the database record

toDateString Tue **Oct** **10** 1950    // converted to date string neither change the day nor the month

date string converted to date **1950-10-10**T00:00:00.000Z    // date in iso format

day extracted from date **10**          // got day unchanged

month extracted from date **9**         // got month -1 as expected

**1950-9-10**    // date in format for the form input date (with trimmings that will have to be removed)

What am I missing?

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2

Answers


  1. Chosen as BEST ANSWER
    0

    That is how I managed to solve it, at least for know. On a later stage I eventually use a Library. But not for now.

    export function dateToPug(dateIso) {

    const date = new Date(dateIso)
    
    let day = (date.getUTCDate())// + 1)
    day < 10 ? day =`0${day}` : ''
    
    let month = (date.getUTCMonth() + 1) 
    month < 10 ? month = `0${month}` : ''
    
    const year = date.getUTCFullYear()

    return `${year}-${month}-${day}`

}

  2. 0

    You are not accounting for timezone differences.

    I added this line to your function

     console.log('getTimezoneOffset',date.getTimezoneOffset())

    and tested with node.js:

    > dateToPug("1950-10-10T00:00:00.000Z")

date string from db 1950-10-10T00:00:00.000Z

toDateString Mon Oct 09 1950

getTimezoneOffset 300
date string converted to date 1950-10-10T00:00:00.000Z

day extracted from date 9

month extracted from date 9

1950-9-9

'1950-9-9'

    getDate() returns 1-31, i.e. the actual day of the month, while getMonth() returns 0-11, i.e. month – 1, so this is correctly indicating month 9 day 9 for the noted timezone offset.

    Note that 12:00 am on Oct 10 in London(UTC) is still Oct 9 for the entire western hemisphere.

    The date functions default to using the local system timezone. Depending on how you are running the code, you may need to explicitly specify a timezone setting to get that to behave the way you want.

    Or just leverage the years of work by other people who have already worked on this problem, and use a datetime library.

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