A timestamp is a way of recording the exact date and time something happened. It's commonly used in computers, databases, websites, and applications to keep track of events like when a file was created, when a message was sent, or when a record was updated. Timestamps help keep everything in the right order and allow systems to sync and sort information accurately.

A Unix timestamp is a number that represents the number of seconds that have passed since January 1, 1970, at 00:00:00 UTC. This starting point is known as the Unix Epoch. Unix time is widely used in programming because it's a simple, consistent way to track time across different systems, regardless of timezones or formats.

The Unix Epoch was chosen because it was a convenient fixed point in time when early Unix systems were developed. It simplifies time calculations by using a zero point — similar to how a ruler starts at zero. From that moment forward, time is just counted in whole seconds (or milliseconds/microseconds), which makes storing and comparing time values fast and efficient.

Timestamps are used everywhere: in software logs to record when actions happen, in databases to track updates, in emails to show when messages were sent, and in web apps to sort and filter information by time. They’re essential for syncing events, maintaining order, detecting changes, and even scheduling tasks like backups or reminders.

A Unix timestamp is a numeric value like 1712236800, which isn’t easily readable by humans but is great for machines. On the other hand, ISO 8601 is a standardized string format like 2025-04-04T12:00:00Z that shows the full date and time in a way that's clear to people. Both formats are common, but used in different contexts depending on readability needs.

While Unix timestamps normally count in seconds, some systems need more precision. Milliseconds add three digits (e.g. 1712236800000) and microseconds add six digits (e.g. 1712236800000000). These formats are useful in high-speed applications like trading systems, performance monitoring, or anywhere events happen very quickly and need precise tracking.

Timestamps are usually stored in UTC (Coordinated Universal Time) to avoid timezone confusion. When a timestamp is displayed to a user, it’s then converted to their local timezone. This ensures consistency across systems but also means the same timestamp can show a different time depending on where you are in the world.

In older 32-bit systems, Unix timestamps are limited to values up to 2147483647, which corresponds to January 19, 2038. After that, the counter overflows — a problem known as the Year 2038 Problem. Modern systems use 64-bit integers, allowing timestamps to represent dates billions of years in the future.

You can convert a date to a Unix timestamp using code (like `Date.now()` in JavaScript or `datetime.timestamp()` in Python) or with online tools. The conversion process involves calculating how many seconds (or milliseconds) have passed between your chosen date and the Unix Epoch (January 1, 1970, UTC).

Both UTC (Coordinated Universal Time) and GMT (Greenwich Mean Time) are time standards used globally. Technically, UTC is the modern, precise atomic time standard, while GMT is an older term based on Earth's rotation. In everyday use, they refer to the same time, but UTC is more accurate and is the official standard in computing and international communication.