If you work with databases, APIs or system logs, you've probably already come across a date in the form of a strange number like 1719577200. This number is a Unix timestamp: a universal way to represent a date and time, understood by every programming language and system.
What is a Unix timestamp?
The Unix timestamp (also called "epoch time") represents the number of seconds elapsed since January 1, 1970 at 00:00:00 UTC, a reference instant called the "Unix epoch". Every possible date and time, past or future, thus corresponds to a unique number, positive after this reference date.
Why use this format instead of a regular date?
- Universality: a simple integer is understood the same way in every programming language, with no format ambiguity (unlike "03/04/2024", which can mean April 3rd or March 4th depending on the country's convention).
- Simplified calculations: comparing two dates, calculating a duration or sorting events chronologically becomes a simple arithmetic operation on numbers, faster and more reliable than handling text strings.
- Timezone independence: a timestamp represents a precise instant in time, regardless of the user's timezone; it's only when displaying it that you convert it to the desired timezone.
Where do you encounter Unix timestamps?
This format is everywhere in databases (creation or modification date field), web APIs (event timestamping), system logs (server logs) and many programming languages that use it internally to represent time (JavaScript, Python, PHP, etc.).
Seconds or milliseconds? A common pitfall
Some systems (notably JavaScript) conventionally use a timestamp in milliseconds rather than seconds, which multiplies the number by 1000. A timestamp in seconds for a 2024 date has 10 digits; in milliseconds, 13 digits. If your converted date looks totally inconsistent (a date in the year 50000, for instance), check whether you've mixed up the two units.
The method, step by step
- To convert a timestamp to a readable date: enter the number, and instantly get the corresponding date and time.
- To convert a date to a timestamp: select a date and time, and get the corresponding Unix number of seconds, ready to use in your code or database.
In summary
The Unix timestamp is a technical but essential format for anyone developing applications or handling data. A quick converter saves tedious manual calculations and the timezone or unit (seconds/milliseconds) errors that often come with them.
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