Convert Unix timestamps to human-readable dates and vice versa. Supports both seconds and milliseconds.
Unix Timestamp, also called Epoch Time or POSIX Time, is the number of seconds (or milliseconds) that have elapsed since January 1, 1970, 00:00:00 UTC. It provides a universal, timezone-independent way to represent a specific moment in time. Unix timestamps are one of the most fundamental concepts in computing—every operating system, programming language, and database uses them internally. Unlike human-readable date formats that vary by region and locale, Unix timestamps are consistent everywhere. A timestamp of 1704067200 represents exactly the same moment in Tokyo, New York, London, and Sydney—the only difference is how you display it in the local timezone. This universal standard makes Unix timestamps ideal for storing dates in databases, recording event times in logs, and coordinating time across distributed systems.
The Unix Epoch (January 1, 1970, 00:00:00 UTC) was chosen somewhat arbitrarily—it marked a round number in the POSIX standards development. All Unix timestamps are relative to this moment. A timestamp of 0 represents midnight UTC on January 1, 1970. A timestamp of 86400 (24 hours × 60 minutes × 60 seconds) represents midnight UTC on January 2, 1970. Negative timestamps represent times before the epoch, though they're rarely used. The current timestamp is roughly 1.7 billion seconds, representing the current time in March 2026. The advantage of this linear representation is that comparing timestamps is trivial—simply compare the numbers. A timestamp of 1000 is definitely before 2000. This makes Unix timestamps perfect for databases, sorting, and calculations.
Seconds vs Milliseconds: Traditional Unix timestamps use seconds, allowing representation of dates from 1970 to the year 2038 (the Y2K38 problem). JavaScript and some modern systems use milliseconds instead, multiplying the timestamp by 1000. A timestamp of 1704067200 (seconds) equals 1704067200000 (milliseconds). This tool supports both formats—select the appropriate unit for your system. Modern systems increasingly prefer seconds for compactness and to avoid the Y2K38 problem.
Timezone-Independent Storage: One crucial advantage of Unix timestamps is timezone independence. Storing "2026-03-11 10:00:00" is ambiguous—10 AM in which timezone? Storing 1710159600 (the timestamp for that moment in UTC) is unambiguous. When displaying this timestamp to users, convert it to their local timezone. This separation of storage and display is crucial for applications serving users worldwide.
This tool provides two-way timestamp conversion. The top section shows the current Unix timestamp, updating every second so you can see it increment in real-time. The first conversion panel converts from Unix timestamps to human-readable dates. Enter any Unix timestamp (in seconds or milliseconds—toggle the checkbox to specify), and click "Convert →" to see the date in local time, UTC time, and ISO 8601 format. The second conversion panel does the opposite: select a date and time using the date picker, then click "Convert →" to see the Unix timestamp in both seconds and milliseconds. This is useful when you need to find the timestamp for a specific date. Use the copy buttons to quickly copy results to your clipboard. The tool handles all valid timestamps from the distant past to the far future.
Database Timestamps: Databases store creation and modification times as Unix timestamps. When a user creates an account at 2026-03-11 10:30:00 UTC, the database records 1710161400. This universal format works across servers in different timezones. When retrieving records, the application converts the timestamp to the user's local timezone for display, but storage remains consistent.
API Requests and Responses: REST APIs use timestamps extensively. A request with a timestamp parameter specifies exactly when something should happen, regardless of server location. API responses include timestamps for events—a social media post's timestamp is universal, displaying as "2 hours ago" calculated from the current timestamp minus the post's timestamp.
Log Analysis and Monitoring: Application logs include timestamps for every event. Tools parse these timestamps to analyze patterns, measure response times, or identify when problems occurred. Sorting by timestamp is instant and accurate because they're simply numbers. Correlating events across multiple servers is trivial when all use Unix timestamps.
Scheduled Tasks and Cron Jobs: Scheduling systems calculate when to execute tasks using timestamps. A task scheduled for "tomorrow at 9 AM" is converted to a specific Unix timestamp representing that moment, then the scheduler checks if the current timestamp has passed that value to trigger execution.
Authentication and Security: Login tokens often include issue and expiration timestamps. Comparing the current timestamp to the token's expiration timestamp determines if the token is still valid. This is fast and reliable across all systems and languages.
The Y2K38 problem is a well-known limitation: 32-bit signed integers can represent values from -2,147,483,648 to 2,147,483,647. Unix timestamps in seconds fit into 32 bits, representing dates from 1901 to 2038. On January 19, 2038, at 03:14:07 UTC, 32-bit timestamps will overflow. Systems that haven't migrated to 64-bit timestamps will malfunction. The solution is straightforward—use 64-bit integers for timestamps, which can represent dates trillions of years in the future. Most modern systems have already made this transition. When building new systems, always use 64-bit timestamps to avoid this problem entirely.
ISO 8601 Format: This tool displays timestamps in ISO 8601 format (e.g., 2026-03-11T10:30:00.000Z), the international standard for date and time representation. This format is unambiguous, sortable as strings, and easily parsed by all modern systems. Use ISO 8601 for APIs, data exchange, and international applications.
Leap Seconds: Unix timestamps don't account for leap seconds—occasional one-second adjustments coordinated between atomic and solar time. This is intentional; leap seconds are handled separately. Unix timestamps remain simple linear counters, and leap seconds are managed at the system level, usually by repeating or skipping a second.
JavaScript's Date Object: JavaScript's Date object uses milliseconds internally, so timestamps are 1000x larger than Unix timestamps. When working with JavaScript, remember to convert: Math.floor(Date.now() / 1000) gives you Unix seconds from JavaScript's millisecond timestamp.
Q: Is Unix timestamp the same as milliseconds since epoch?
A: No. Unix timestamp traditionally means seconds since epoch. Milliseconds since epoch is 1000 times larger. JavaScript uses milliseconds by default, while most other systems use seconds. Always verify which unit your system uses—check documentation or test with a known date.
Q: Can timestamps represent times before 1970?
A: Yes, using negative timestamps. However, most systems treat timestamps as unsigned 32 or 64-bit integers, not supporting negative values. For historical dates before 1970, use different date representations like ISO 8601 strings.
Q: How do I handle timezone conversions?
A: Timestamps are timezone-independent—they represent universal moments. To display in a specific timezone, convert the timestamp to that timezone using your programming language's date libraries (Date in JavaScript, datetime in Python, etc.). Always store in timestamps, convert for display.
Q: Why use timestamps instead of date strings?
A: Timestamps are compact (smaller data), sortable directly, timezone-independent, and math-friendly (adding 86400 to any timestamp adds one day). Date strings are human-readable but require parsing and are ambiguous without timezone information.
Q: How precise are timestamps?
A: Second-resolution timestamps are precise to the nearest second. Millisecond-resolution timestamps are precise to the nearest millisecond. For higher precision, use microseconds (JavaScript lacks native support). One second might seem imprecise, but it's adequate for logging, scheduling, and database operations.
Q: Will timestamps break on January 19, 2038?
A: Only systems still using 32-bit signed timestamps. Modern systems use 64-bit timestamps, good for billions of years. Legacy systems built on 32-bit timestamps will fail at the year 2038 threshold unless updated. Check your systems now if they're built on older architecture.
Always Use Timestamps for Storage: When storing dates in databases or systems, always use Unix timestamps. They're standardized, efficient, and reliable. Only convert to human-readable formats for display to users. This ensures consistency across your entire system.
Specify the Unit Explicitly: When sharing timestamps, always specify whether they're in seconds or milliseconds. The same 10-digit number is completely different depending on the unit. Documentation should be clear about this—it prevents subtle bugs that are hard to find.
Test at Boundaries: Test date-related code around DST transitions, year boundaries, and the Y2K38 threshold (if applicable). These edge cases often reveal bugs in date handling logic that aren't obvious in normal testing.
Use Timezone-Aware Libraries: When working with dates and times in code, use proper timezone-aware libraries (moment-timezone, pytz, etc.) rather than manual calculations. These libraries handle all the edge cases and variations correctly.