Unix Timestamp Explained: What Epoch Time Is and How to Convert It

Unix timestamps are numeric values representing specific moments in time. They indicate the number of seconds that have passed since a specific starting point, known as the Unix epoch, which is January 1, 1970 at 00:00:00 UTC. This single numeric value makes it simple for computers to store, compare, and transmit dates without the need for various human-readable date formats.

Developers frequently use Unix timestamps in APIs, databases, application logs, JWT tokens, authentication systems, cloud applications, cron jobs, scheduling, file metadata, and distributed systems. Comparing two timestamps is straightforward, as a larger timestamp signifies a later point in time. For instance, comparing timestamp A and timestamp B, where timestamp A is less than timestamp B, means that A occurred before B.

There is a common mistake when dealing with Unix timestamps: distinguishing between seconds and milliseconds. A timestamp in seconds may appear as 1757894400, while a timestamp in milliseconds appears as 1757894400000. The latter is 1,000 times larger because there are 1,000 milliseconds in a single second. In JavaScript, the Date.now() method provides timestamps in milliseconds, and Math.floor(Date.now() / 1000) converts it to seconds.

JavaScript's Date object can be utilized to work with Unix time. To get the current timestamp in milliseconds, use Date.now(). To convert a Unix timestamp back into a JavaScript Date object, multiply it by 1000. Conversely, Python's time module facilitates Unix timestamp operations. To get the current Unix timestamp in Python, import time and use int(time.time()).

To convert a timestamp into a readable UTC date, import datetime and timezone from the datetime module, then use datetime.fromtimestamp(timestamp, tz=timezone.utc).

Linux systems make it easy to work with Unix timestamps from the command line. To get the current timestamp, use the command date +%s. To convert a Unix timestamp into a readable date, use date -d @1757894400. When working with APIs or logs, always verify if the application expects seconds or milliseconds to avoid incorrect date conversions.