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JayCooper's avatar
JayCooper
Community Member
3 years ago

JavaScript to Subtract Days from Current Date

I'm working on a course that involves sorting juveniles with one of the criteria being their age.  I'm looking to display each child's age based on the current date, minus X number of days so that t...
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Jürgen_Schoene_'s avatar
Jürgen_Schoene_
Community Member
3 years ago

here is a javascript example

const years = -18; // 18 years back
const days  = +10; // 10 day forward

const event = new Date();
event.setFullYear(event.getFullYear() + years);
event.setDate(event.getDate() + days)

const options = { 
  weekday: 'long',
  year: 'numeric', 
  month: 'long', 
  day: 'numeric' 
};
const result = event.toLocaleDateString('en-US', options);

// 'en-US' -> "Saturday, February 26, 2005"
// 'en-GB' -> "Saturday, 26 February 2005"
// 'de-DE' -> "Samstag, 26. Februar 2005"

more info for Date and toLocaleDateString

JayCooper's avatar
JayCooper
Community Member
3 years ago

Jurgen,

Thank you for the help.  The problem with breaking the new Date up this way is how to make adjustments if the date is at the beginning of the month or year.  

I appreciate your help.

v/r

Jay

  • Jürgen_Schoene_'s avatar
    Jürgen_Schoene_
    Community Member
    3 years ago

    you have nothing to adjust - the javascript library does all adjustments automaticly,
    this is modern JavaScript

    const years = -18; // 18 years back
    const days  = +10; // 10 day forward

    const options = { 
      weekday: 'long',
      year: 'numeric', 
      month: 'long', 
      day: 'numeric' 
    };

    const event = new Date( 'December 28, 2023 23:15:30');
    console.log( "1 - now", event.toLocaleDateString('en-US', options) )

    event.setFullYear(event.getFullYear() + years);
    console.log( "2 - year", years, event.toLocaleDateString('en-US', options) )

    event.setDate(event.getDate() + days)
    console.log( "3 - days", days, event.toLocaleDateString('en-US', options) )

    result:

    • "1 - now", "Thursday, December 28, 2023"
    • "2 - year", -18, "Wednesday, December 28, 2005"
    • "3 - days", 10, "Saturday, January 7, 2006"

    or with February 29

    const event = new Date( 'February 29, 2024 23:15:30');
    console.log( "1 - now", event.toLocaleDateString('en-US', options) )

    event.setFullYear(event.getFullYear() + years);
    console.log( "2 - year", years, event.toLocaleDateString('en-US', options) )

    event.setDate(event.getDate() + days)
    console.log( "3 - days", days, event.toLocaleDateString('en-US', options) )

    result:

    • "1 - now", "Thursday, February 29, 2024"
    • "2 - year", -18, "Wednesday, March 1, 2006"
    • "3 - days", 10, "Saturday, March 11, 2006"


      or the same date, but -16 years
    • "1 - now", "Thursday, February 29, 2024"
    • "2 - year", -16, "Friday, February 29, 2008"
    • "3 - days", 10, "Monday, March 10, 2008"

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