Javascript – All about datetime

date-fns

How to convert UTC time to EAST?

import { formatToTimeZone } from 'date-fns-timezone';
...
// From: 2020-10-02T05:43:00Z
// To: 2020-10-02 15:43:00
formatToTimeZone('2020-10-02T05:43:00Z', 'YYYY-MM-DD HH:mm:ss', { timeZone: 'Australia/Melbourne' });

How to convert time string to Date instance?

// Date time needs to have this format: 'YYYY-MM-DD HH:mm:ss'
new Date(yourString)

How to convert string to plain Javascript time object and vice versa?

import { parse } from 'date-fns';

// "2021-10-04 16:59:03.000" to "3368473269"
const comparedDate = parse(
  yourString,
  'yyyy-MM-dd HH:mm:ss.SSS',
  new Date(),
).getTime();

import { format } from 'date-fns';

// "3368473269" to "2021-10-04 16:59:03.000"
const comparedDate = format(timeObjString, 'yyyy-MM-dd HH:mm:ss.SSS');

How to get seconds difference between 2 date time?

// Between future and current time
differenceInSeconds(new Date(futureTimeString), new Date())

How to format today date?

import { format } from 'date-fns';
const today = format(new Date(), 'yyyy-MM-dd') // 2021-02-12

How to convert date string to fns date?

import { parse } from 'date-fns';
const fnsDate = parse('2021-02-15', 'yyyy-MM-dd', new Date());

How to get day difference between 2 date strings?

import { format, differenceInDays, parse } from 'date-fns';

// 2021-09-10 and today

const comparedDate = parse('2021-09-10', 'yyyy-MM-dd', new Date());
const todayWithoutTime = new Date(
  new Date().getFullYear(),
  new Date().getMonth(),
  new Date().getDate(),
);
const dayDifference = differenceInDays(comparedDate, todayWithoutTime);
if (dayDifference === 1) {
  console.log('Tomorrow')
} else {
  console.log(dayDifference)
}

momentJs

How to format current date?

moment(new Date()).format("DD/MM/YYYY")

How to format current date to UTC?

import moment from 'moment-timezone'
export const getCurrentUTCTime = () => {
    const utcMoment = moment.utc().format('YYYY-MM-DDTHH:mm:ss')
    return utcMoment + 'Z'
}

How to convert UTC back to local time?

import moment from 'moment-timezone'
export const convertUTCtoLocalFormat = (utcTime: string, format: string) => {
    const momentTime = moment(utcTime)
    return momentTime.tz('Australia/Melbourne').format(format)
}

How to format date string?

export const formatDate = (
  dateTime: string,
  inputFormat: string,
  outputFormat: string
) => {
  const mom = moment(dateTime, inputFormat) // 2021-08-21
  return mom.format(outputFormat) // 02 Aug 21
}

How to convert string to moment time

// Normal time string
const momentTime = Moment(strTime);

// UTC time string
const momentTime = Moment.utc(strTimeUtc);

Compare and sort moment time array

allTimeTable.sort((a, b) => {
  const aTime = Moment.utc(a.utc_time);
  const bTime = Moment.utc(b.utc_time);
  if (aTime.isBefore(bTime)) {
    return -1;
  } else if (aTime.isAfter(bTime)) {
    return 1;
  }
  return 0;
});

How to calculate time difference in hours?

    const startTime = Moment(reduxLastUpdate);
    const endTime = Moment();
    const duration = Moment.duration(endTime.diff(startTime));
    const hours = duration.asHours();

How to calculate days difference?

var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 28]);
a.diff(b, 'days')

Plain JavaScript

How to convert UTC time to unix?

Date.parse(utcTimeString)

How to add 2 hours to Date object?

const now = new Date();
now.setHours( now.getHours() + 2 );     // 1589857034624

// Test
new Date(1589857034624)

This solution can’t be applied to float value. This means you can’t use “now.getHours() + 1.5” => This still returns 1 hour, not 1.5 hour

How to add minutes to Date object?

const now = new Date();
const next30mins = new Date(now.getTime() + 30*60000);

How to create a timer countdown?

Create a 60 seconds countdown timer

    let timeLeft = 60
    const timer = setInterval(function(){
      if (timeLeft <= 0) {
        clearInterval(timer)
      }
      
      document.getElementById("countdown-text").innerHTML = timeLeft
      
      timeLeft -= 1
    }, 1000)