Working With Dates

Dates and times are very important in any programming language. JavaScript has a Date object that represents a point in time and let's you do some basic operations on it.

We can instantiate a Date object with the new keyword.

let d;
d = new Date(); // Fri Jul 22 2022 08:35:10 GMT-0400

If do not include any arguments, the Date object will be set to the current date and time and you will also get the timezone information. Sometimes you will need to specify the timezone because it can cause some weird issues.

Converting to a string

If we look at the type of the variable, it will show object. You can always convert it to a string using the toString() method.

console.log(typeof d); // object

d.toString(); // "Fri Jul 22 2022 08:35:10 GMT-0400"

console.log(typeof d); // string

Specific dates

If you want a specific date and time, you can pass in the year, month, day, hour, minute, second, and millisecond.

One caveat is that the month is 0-indexed, so January is 0 and December is 11.

d = new Date(2022, 6, 10); // Fri Jul 10 2022 00:00:00 GMT-0400

If you want to add a time, you can. Let's make it 12:30:00.

d = new Date(2022, 6, 10, 12, 30, 0); // Fri Jul 10 2022 12:30:00 GMT-0400

You can also pass in different date/time strings. You would use the actual month number here.

d = new Date('2022-07-10T12:30:00'); // July 10, 2022 12:30:00
d = new Date('07/10/2022 12:30:00'); // July 10, 2022 12:30:00
d = new Date('2022-07-10 12:30:00'); // July 10, 2022 12:30:00

You can pass a date without time as well.

Note that if you use the YYYY-MM-DD format with hyphens, it may be one day off due to timezones.

d = new Date('2022-07-10'); // May be July 09, 2022

If you use the MM-DD-YYYY format, it should not have this issue.

d = new Date('07-10-2022'); // July 10, 2022

// Backslashes will also work
d = new Date('07/10/2022'); // July 10, 2022

Timestamps

The UNIX timestamp is a system for describing a point in time. It is an integer that represents the number of seconds elapsed since January 1 1970 (An arbitrary date).

The timestamp in JavaScript is expressed in milliseconds.

You can get the current timestamp using:

Date.now(); // 1658497991311

To get the timestamp of a specific date, you can use the getTime() or the valueOf method.

d = new Date('07/22/2022'); // July 10, 2022
d.getTime(); // 1658497991311
d.valueOf(); // 1658497991311

You can also create date objects from a timestamp.

d = new Date(1658497991311); // Fri Jul 22 2022 08:35:10 GMT-0400

The JavaScript timestamp is expressed in milliseconds. To convert it to seconds:

Math.floor(Date.now() / 1000); // 1658498058