JavaScript Date Object Cheatsheet

The Date object in JavaScript is used to work with dates and times. It provides methods to create, manipulate, and format date and time values.

Creating Dates

You can create a Date object in multiple ways:

Current Date and Time:

   const now = new Date();
   console.log(now); // Current date and time

Specific Date:

   const specificDate = new Date(2024, 10, 21); // Year, Month (0-based), Day
   console.log(specificDate); // Thu Nov 21 2024

From a String:

   const fromString = new Date("2024-11-21T10:00:00");
   console.log(fromString); // Thu Nov 21 2024 10:00:00 GMT

From Timestamps (milliseconds since Unix epoch):

   const fromTimestamp = new Date(1732231200000);
   console.log(fromTimestamp); // Thu Nov 21 2024 10:00:00 GMT

Common Methods

Getting Date and Time

Method	Description	Example
`getFullYear()`	Returns the year	`date.getFullYear()` -> `2024`
`getMonth()`	Returns the month (0-11)	`date.getMonth()` -> `10` (November)
`getDate()`	Returns the day of the month (1-31)	`date.getDate()` -> `21`
`getDay()`	Returns the weekday (0-6, Sun=0)	`date.getDay()` -> `4` (Thursday)
`getHours()`	Returns the hour (0-23)	`date.getHours()` -> `10`
`getMinutes()`	Returns the minutes (0-59)	`date.getMinutes()` -> `0`
`getSeconds()`	Returns the seconds (0-59)	`date.getSeconds()` -> `0`
`getTime()`	Returns timestamp in milliseconds	`date.getTime()` -> `1732231200000`

Setting Date and Time

Method	Description	Example
`setFullYear(year)`	Sets the year	`date.setFullYear(2025)`
`setMonth(month)`	Sets the month (0-11)	`date.setMonth(0)` -> January
`setDate(day)`	Sets the day of the month	`date.setDate(1)` -> First day of the month
`setHours(hour)`	Sets the hour (0-23)	`date.setHours(12)`
`setMinutes(minutes)`	Sets the minutes (0-59)	`date.setMinutes(30)`
`setSeconds(seconds)`	Sets the seconds (0-59)	`date.setSeconds(45)`

Formatting Dates

Method	Description	Example
`toDateString()`	Returns date as a human-readable string	`date.toDateString()` -> `"Thu Nov 21 2024"`
`toISOString()`	Returns date in ISO format	`date.toISOString()` -> `"2024-11-21T10:00:00.000Z"`
`toLocaleDateString()`	Returns date in localized format	`date.toLocaleDateString()` -> `"11/21/2024"`
`toLocaleTimeString()`	Returns time in localized format	`date.toLocaleTimeString()` -> `"10:00:00 AM"`

Common Use Cases

Calculate Days Between Two Dates:

   const startDate = new Date("2024-11-01");
   const endDate = new Date("2024-11-21");
   const diffInTime = endDate - startDate; // Difference in milliseconds
   const diffInDays = diffInTime / (1000 * 60 * 60 * 24); // Convert to days
   console.log(diffInDays); // 20

Countdown Timer:

   const targetDate = new Date("2024-12-31T23:59:59");
   setInterval(() => {
       const now = new Date();
       const timeLeft = targetDate - now; // Milliseconds left
       const days = Math.floor(timeLeft / (1000 * 60 * 60 * 24));
       const hours = Math.floor((timeLeft / (1000 * 60 * 60)) % 24);
       const minutes = Math.floor((timeLeft / (1000 * 60)) % 60);
       const seconds = Math.floor((timeLeft / 1000) % 60);
       console.log(`${days}d ${hours}h ${minutes}m ${seconds}s`);
   }, 1000);

Format Current Date:

   const now = new Date();
   const formatted = `${now.getFullYear()}-${now.getMonth() + 1}-${now.getDate()}`;
   console.log(formatted); // "2024-11-21"

Find the Day of the Week:

   const date = new Date("2024-11-21");
   const days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
   console.log(days[date.getDay()]); // "Thursday"

Check Leap Year:

   const isLeapYear = (year) => {
       return (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0);
   };
   console.log(isLeapYear(2024)); // true

Add/Subtract Days:

   const addDays = (date, days) => {
       const result = new Date(date);
       result.setDate(result.getDate() + days);
       return result;
   };
   console.log(addDays(new Date(), 10)); // Adds 10 days to the current date

Pro Tips

Use Date.now() to get the current timestamp directly without creating a Date object:

   console.log(Date.now()); // Timestamp in milliseconds

Be mindful of time zones when working with dates across regions. Use libraries like Moment.js or Day.js for advanced handling.
To avoid month off-by-one errors, remember that months are 0-indexed (0 = January, 11 = December).

Blog

JavaScript Date Object Cheatsheet

Nwafor Onyebuchi

Creating Dates

Common Methods

Getting Date and Time

Setting Date and Time

Formatting Dates

Common Use Cases

Pro Tips

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