JavaScript Date Object

Using the new Date() Constructor

const date = new Date();
console.log(date);

//OUTPUT
Sun Sep 10 2023 23:12:45 GMT+0530 (India Standard Time)

Passing Individual Date Components

/**
 Let's understand the arguments passed.
 Starting from the left to right,
   - 2023 represents the Year
   - 8 represents the Month. It is an idex value starts 
     with 0 which repreents January month in the English
     calendar, 1 for February, and so on.
   - 10 represents the day between 1 to 31.
   - 23 represents the hour between 1 to 24.
   - 15 represents the minute.
   - 34 represents the second.
   - 0 represent the millisecond.

*/
const date = new Date(2023, 8, 10, 23, 15, 34, 0);
console.log(date);


//OUTPUT
Sun Sep 10 2023 23:15:34 GMT+0530 (India Standard Time)

Parsing string to a JavaScript Date

const date = new Date("2013-09-10T13:24:00");
console.log(date);


//OUTPUT

Tue Sep 10 2013 13:24:00 GMT+0530 (India Standard Time)

Using Timestamps

const date = new Date(1688737100000);
console.log(date);


//OUTPUT
Fri Jul 07 2023 19:08:20 GMT+0530 (India Standard Time)

get the current date

Current date using JavaScript Date Methods

const date = new Date();

date.getFullYear(); // 2023
date.getMonth(); // 8
date.getDate(); // 11

const date = new Date();

const day = date.getDate();
const month = date.getMonth() + 1; // The month index starts from 0
const year = date.getFullYear();

let currentDate = `${day}/${month}/${year}`;
console.log(currentDate); // 10/9/2023


OR

let currentDate = `${year}-${month}-${day}`;


OR

const month = String(date.getMonth()+1).padStart(2,"0"); // Output "09"

Current date using the now() method

new Date(Date.now()); // Mon Sep 11 2023 08:01:44 GMT+0530 (India Standard Time)

new String(new Date(Date.now())).slice(4, 15); // "Sep 11 2023"

Current Date using the toJSON() method

new Date().toJSON(); // "2023-09-11T02:41:56.619Z"

new Date().toJSON().slice(0, 10); // "2023-09-11"

Current Date using the toLocaleDateString() method

const date = new Date().toLocaleDateString();
console.log(date); // "11/09/2023"



const date = new Date().toLocaleDateString("de-DE");
console.log(date); // 17.6.2022

How to calculate elapsed time

// Define two Date objects representing the start and end dates
const startDate = new Date('2023-08-15T00:00:00');
const endDate = Date.now(); // Current date and time in milliseconds

// Calculate the time difference in milliseconds
const timeDifferenceMS = endDate - startDate;

// Calculate the elapsed time in seconds, minutes, hours, and days
const timeDifferenceSecs = Math.floor(timeDifferenceMS / 1000);
const timeDifferenceMins = Math.floor(timeDifferenceMS / 60000);
const timeDifferenceHours = Math.floor(timeDifferenceMS / 3600000);
const timeDifferenceDays = Math.floor(timeDifferenceMS / 86400000);

console.log(`Time difference in milliseconds: ${timeDifferenceMS}`);
console.log(`Time difference in seconds: ${timeDifferenceSecs}`);
console.log(`Time difference in minutes: ${timeDifferenceMins}`);
console.log(`Time difference in hours: ${timeDifferenceHours}`);
console.log(`Time difference in days: ${timeDifferenceDays}`);

Date diff

let date1 = new Date("01/16/2024");
let date2 = new Date("01/26/2024");

// Convert dates to UTC timestamps
let utc1 = Date.UTC(date1.getFullYear(), date1.getMonth(), date1.getDate());
let utc2 = Date.UTC(date2.getFullYear(), date2.getMonth(), date2.getDate());

// Calculate the time difference in milliseconds
let timeDiff = Math.abs(utc2 - utc1);

// Convert milliseconds to days
let daysDiff = Math.ceil(timeDiff / (1000 * 60 * 60 * 24));

// Display the result
console.log(`Total number of days between dates:
${date1.toDateString()} and ${date2.toDateString()} is: ${daysDiff} days`);


//OUTPUT

Total number of days between dates:
Tue Jan 16 2024 and Fri Jan 26 2024 is: 10 days

Add Days to Current Date

// Get current date
var date = new Date();

// Add five days to current date
date.setDate(date.getDate() + 5);

console.log(date);



// Specific date
var date = new Date('August 21, 2021 16:45:30');

// Add ten days to specified date
date.setDate(date.getDate() + 10);

console.log(date);

Compare Dates

// Create two Date objects
const firstDate = new Date('2024-02-06T12:00:00');
const secondDate = new Date('2024-02-07T12:00:00');

// Convert the dates to ISO strings
const firstISODate = firstDate.toISOString();
const secondISODate = secondDate.toISOString();


// Compare the two ISO strings
if (firstISODate === secondISODate) {
  console.log("The dates are equal.");
} else if (firstISODate < secondISODate) {
  console.log("firstDate is before secondDate.");
} else {
  console.log("firstDate is after secondDate.");
}

JavaScript Date Formatting

const date = new Date(Date.UTC(2013, 09, 17, 13, 10, 20));

console.log("In en-US: ", new Intl.DateTimeFormat("en-US").format(date));  // In en-US:  10/17/2013

console.log("In en-GB: ", new Intl.DateTimeFormat("en-GB").format(date)); // In en-GB:  17/10/2013

console.log("In ko-KR: ", new Intl.DateTimeFormat("ko-KR").format(date)); // In ko-KR:  2013. 10. 17.

Example 1

function  date_last_performed1(){
		 d1=$('.date_last_performed2').val();
		 d2=$('.date_last_performed1').val();

		 dd1='';
		 if(d1!='' && d2!=''){
			
			fd=new Date(d1);			
			fd.setMonth(fd.getMonth()+parseInt(d2));

			td=fd.getDate();
			tm=fd.getMonth()+1;
			ty=fd.getFullYear();

			dd1=tm+"-"+td+"-"+ty;			

		 }		 
				
		$('.date_last_performed3').val(dd1);
	}

Example 2

function calculateDates(){
      let installed_date=$('#installed_date').val();
      var warranty_days=$('.warranty_id option:selected').attr("data-days");     
      var maintenance_days=$('.maintenance_id option:selected').attr("data-days"); 

      if(installed_date!=''){

            installed_date=installed_date.split("-");
            if(warranty_days>0){
                  
                  wanrrantyEndDate=new Date(installed_date[2]+"-"+installed_date[1]+"-"+installed_date[0]);                 
                  wanrrantyEndDate.setDate(wanrrantyEndDate.getDate()+parseInt(warranty_days)-1);
                 

                  wanrrantyEndDate=wanrrantyEndDate.getDate()+"-"+(wanrrantyEndDate.getMonth()+1)+"-"+wanrrantyEndDate.getFullYear();                  
                  $('.warranty_end_date').val(wanrrantyEndDate);
            }

            if(maintenance_days>0){
                  maintenanceEndDate=new Date(installed_date[2]+"-"+installed_date[1]+"-"+installed_date[0]);
                  maintenanceEndDate.setDate(maintenanceEndDate.getDate()+parseInt(maintenance_days)-1);

                  maintenanceEndDate=maintenanceEndDate.getDate()+"-"+(maintenanceEndDate.getMonth()+1)+"-"+maintenanceEndDate.getFullYear();
                  $('.next_pm_date').val(maintenanceEndDate);
            }

      }       


}