What is a Unix Timestamp?
The Unix timestamp (also known as Epoch time or POSIX time) is a universal standard for tracking time in computing. It represents the total number of seconds that have elapsed since 00:00:00 UTC on January 1, 1970 (an arbitrary date chosen by early Unix engineers, known as the Unix Epoch).
Why do Developers Use Epoch Time?
Dealing with timezones, leap years, daylight savings time, and localized date formats (like MM/DD/YYYY vs DD/MM/YYYY) is incredibly complex for software. A Unix timestamp solves this by reducing time to a single, globally uniform integer.
- Database Storage: Storing a single integer in a database is highly efficient and makes querying date ranges incredibly fast.
- Global Synchronization: A Unix timestamp of
1700000000represents the exact same moment in time whether the server is located in Tokyo, New York, or London. The frontend client's browser is responsible for translating that integer into the user's local timezone.
Seconds vs. Milliseconds
A standard Unix timestamp is 10 digits long and counts in seconds. However, modern languages like JavaScript (and environments like Node.js) natively use 13-digit timestamps that count in milliseconds. If your converted date says it is from the year 1970, but you expected the current year, you likely entered a 10-digit timestamp into a function expecting 13 digits.
To fix this in JavaScript, simply multiply the timestamp by 1000 before creating the date object:
// Correct way to handle 10-digit backend timestamps in JavaScript
const backendUnixTimestamp = 1685587200;
const dateObject = new Date(backendUnixTimestamp * 1000);
console.log(dateObject.toLocaleString());