In programming, we often need to deal with dates and times, which can be represented in a few different ways, like an object (via
Why Convert Date or Date String to Timestamp
But why do we need to convert a date or date string to a timestamp in the first place? Timestamps are a more universal way of storing date and time information. They represent the number of seconds (or milliseconds) since the Unix Epoch (January 1, 1970), making them a simple way to store date and time data. They're also timezone-agnostic, which can simplify things when dealing with data from different time zones.
Date object represents a moment in time. You can create a new Date object with the
new Date() constructor.
On the other hand, a timestamp is a numeric representation of a date, as described earlier.
let currentDate = new Date(); console.log(currentDate); // Outputs: 2023-10-04T13:20:23.670Z
How to Convert a Date to Timestamp
getTime() method, which returns the number of milliseconds since the Unix Epoch.
let currentDate = new Date(); let timestamp = currentDate.getTime(); console.log(timestamp); // Outputs: 1696425660603
getTime() method returns the timestamp in milliseconds. If you need the timestamp in seconds, you can divide the result by 1000.
How to Convert a Date String to Timestamp
So what if we have a date in string format? It'll be a similar process as before, but with the extra step of converting the string to a
Date object and then the timestamp.
Just make sure your date string is in a format that the
Date constructor can understand. According to MDN:
Apparently other formats do work, but are implementation-dependent and may not work across all browsers.
let dateString = "2023-10-04"; let dateObject = new Date(dateString); let timestamp = dateObject.getTime(); console.log(timestamp); // Outputs: 1696377600000
So the date string should be in a format recognized by the
Date.parse() method (used internally by the
Date constructor). While the above format is formally specified, you can also use more shorthand dates like "YYYY-MM-DD".
While we've focused on the
Date object and its
valueOf() method returns the primitive value of a
Date object as a number data type, which is the timestamp.
Here's an example:
let date = new Date(); console.log(date.valueOf()); // Output: 1696428432208
+ operator can also be used to convert a
Date object to a timestamp. This works because the
+ operator triggers the
valueOf() method behind the scenes in order to do any mathematical operation on the date.
let date = new Date(); console.log(+date); // Output: 1696428432208
Note: While these methods achieve the same result, it's important to understand how they work and when to use them. The
+ operator, for example, might be less clear to someone reading your code than the explicit
Common Errors and How to Avoid Them
Date object is based on the user's local time zone, but timestamps are always UTC. This can lead to unexpected results if not handled correctly.
For example, let's say you create a
Date object for midnight on a specific date:
let date = new Date('2023-10-04T00:00:00'); console.log(date.getTime()); // Output: 1696428432208
Depending on your local time zone, the timestamp might not represent midnight UTC, but some other time. To avoid this, always create
Date objects in UTC when you plan to convert them to timestamps.
Another common mistake is using the
Date.parse() method to convert a date string to a timestamp. While this can work, it's not recommended because
Date.parse() has inconsistent behavior across different browsers and can lead to some very hard-to-find bugs!
Use-Cases of Date/Timestamp Conversion
Converting dates to timestamps is useful in many situations. For example, timestamps are often used in APIs and databases to record when an event occurred. By storing the time as a timestamp, you can easily compare times and calculate durations—something that's much harder, or more error-prone, with date strings.
Date objects at the start/end of the process, but then you'd need to convert to timestamp to be able to find the difference between the two.
getTime() method. We've also looked at alternative methods, common errors to avoid, and some use-cases for date and timestamp conversion.