How Unix Timestamps Work

What is Unix Time?

Unix time (also called epoch time, POSIX time, or Unix timestamp) is a system for describing points in time. It represents the number of seconds that have elapsed since the "Unix epoch" - January 1, 1970, 00:00:00 UTC - not counting leap seconds.

Timestamp Formats

1. Seconds (10 digits)

The standard Unix timestamp format representing seconds since epoch.

2. Milliseconds (13 digits)

Used in JavaScript and many web applications for higher precision.

3. Microseconds (16 digits)

Used in high-precision systems and some databases.

Conversion Process

Epoch to Date

Converting a Unix timestamp to a human-readable date involves these steps:

1. Identify the timestamp format (seconds, milliseconds, or microseconds)
2. Convert to milliseconds if necessary (JavaScript Date objects use milliseconds)
3. Create a Date object from the timestamp
4. Format the date according to the desired timezone and format

Date to Epoch

Converting a date to Unix timestamp:

1. Parse the input date string or date components
2. Create a Date object (automatically handles timezone conversion to UTC)
3. Get the timestamp in milliseconds using getTime()
4. Convert to seconds by dividing by 1000 (if seconds format is desired)

Timezone Handling

Unix timestamps are always in UTC, but when displaying dates to users, we often need to convert to local timezones:

• UTC: The standard reference timezone (GMT+0)
• Local Time: Adjusted for the user's timezone
• Specific Timezones: Convert to any timezone (EST, PST, JST, etc.)

Common Use Cases

Limitations and Considerations