What is Unix Timestamp?
A Unix timestamp is a numeric representation of time—specifically, the total number of seconds (or milliseconds) that have elapsed since January 1, 1970, 00:00:00 UTC, known as the Unix Epoch. Also called Epoch time, POSIX time, or seconds since epoch, it provides a timezone-independent, universal format for representing any moment in time as a single integer value.
Example:
Timestamp 1767218400 = January 1, 2026, 00:00:00 UTC
This universal format eliminates timezone confusion by always representing time in UTC. Because it's a simple integer, Unix timestamps are easily stored in databases (requiring only 4-8 bytes), compared using basic arithmetic, and transmitted across different computing platforms, programming languages, and systems around the world.
Why is the Unix Epoch January 1, 1970?
The History Behind 1970
The Unix operating system was developed at Bell Labs in the late 1960s. Engineers chose January 1, 1970 (the start of a new decade) as the reference point for Unix timestamps—a practical, round starting point that was close enough to the system's creation date to be convenient yet far enough in the past to avoid immediate overflow issues. This arbitrary decision became the universal standard adopted by all operating systems and programming languages, making 1970 the canonical "beginning of Unix time."
At the Unix Epoch (timestamp 0), the world was entering a new decade. Since then, Unix timestamps have counted every second, reaching over 1.7 billion by 2024. Negative timestamps represent dates before 1970—for example, -86400 represents December 31, 1969.
How Do Unix Timestamps Work?
Unix timestamps work by counting the total number of seconds elapsed since the Unix Epoch (January 1, 1970, 00:00:00 UTC). Every second that passes increments the timestamp value by one. They're always in UTC (never affected by timezone or daylight saving time), stored as simple integers for efficient database storage and comparison, and universally supported by all programming languages and operating systems.
Always UTC
Timestamps are always in Coordinated Universal Time (UTC), making them consistent globally regardless of local timezone.
Simple Integer
Stored as a single number (typically 32-bit or 64-bit integer), making storage efficient and comparisons instant.
No DST Impact
Unaffected by Daylight Saving Time changes. The same timestamp always represents the exact same moment.
Conversion Formula
Date to Timestamp: Calculate seconds between your date and January 1, 1970 00:00:00 UTC
Timestamp to Date: Add the timestamp seconds to January 1, 1970 00:00:00 UTC
How Many Seconds in Common Time Periods?
Quick Reference: 1 minute = 60 seconds, 1 hour = 3,600 seconds, 1 day = 86,400 seconds, 1 week = 604,800 seconds, 1 year = 31,556,926 seconds (accounting for leap years). Understanding these conversions is essential for timestamp calculations and working with Unix epoch time across different systems.
Below is the comprehensive time units reference table for all your timestamp conversion needs:
| Time Period | Seconds | Milliseconds |
|---|---|---|
| 1 Second | 1 | 1,000 |
| 1 Minute | 60 | 60,000 |
| 1 Hour | 3,600 | 3,600,000 |
| 1 Day | 86,400 | 86,400,000 |
| 1 Week | 604,800 | 604,800,000 |
| 1 Month (30.44 days) | 2,629,744 | 2,629,744,000 |
| 1 Year (365.24 days) | 31,556,926 | 31,556,926,000 |
What are the Different Timestamp Precision Formats?
Timestamps are available in four precision levels: Seconds (10 digits, 1704067200—standard for APIs and databases), Milliseconds (13 digits, 1704067200000—JavaScript standard), Microseconds (16 digits—high-precision applications), and Nanoseconds (19 digits—kernel and high-frequency trading). Choose based on your application's timing requirements and storage constraints.
Timestamps can be stored in various precisions depending on your application's needs:
Seconds (Standard)
1704067200
10 digits. Most common format. Used in most APIs and databases.
Milliseconds
1704067200000
13 digits. Used by JavaScript Date.now() and many modern APIs.
Microseconds
1704067200000000
16 digits. High-precision applications, scientific computing.
Nanoseconds
1704067200000000000
19 digits. Used in high-frequency trading, kernel timestamps.
Why Use Unix Timestamps?
Unix timestamps are used because they provide efficient storage (4-8 bytes), enable fast calculations, remain timezone-independent, and are universally supported across all programming languages and databases, making them the industry-standard for backend systems, APIs, and distributed applications.
Database Storage
Efficient datetime storage and retrieval with minimal space (4-8 bytes vs 19+ bytes for ISO 8601).
API Communication
Industry-standard format for RESTful APIs and data exchange between systems.
Log File Analysis
Consistent timestamping across distributed systems and microservices.
Time Calculations
Simple arithmetic for date comparisons, duration calculations, and scheduling.
Performance
Fast comparisons without parsing or string conversion overhead.
Global Consistency
UTC-based, unaffected by timezone changes or daylight saving time.
Programming Language Support
All major programming languages provide native Unix timestamp support:
| Language | Get Current Timestamp | Convert to Date |
|---|---|---|
| JavaScript | Math.floor(Date.now() / 1000) | new Date(timestamp * 1000) |
| Python | int(time.time()) | datetime.fromtimestamp(timestamp) |
| PHP | time() | date('Y-m-d H:i:s', $timestamp) |
| Java | Instant.now().getEpochSecond() | Instant.ofEpochSecond(timestamp) |
| C# | DateTimeOffset.Now.ToUnixTimeSeconds() | DateTimeOffset.FromUnixTimeSeconds(timestamp) |
| Go | time.Now().Unix() | time.Unix(timestamp, 0) |
| Ruby | Time.now.to_i | Time.at(timestamp) |
| Swift | Int(Date().timeIntervalSince1970) | Date(timeIntervalSince1970: timestamp) |
| Rust | SystemTime::now().duration_since(UNIX_EPOCH) | UNIX_EPOCH + Duration::from_secs(timestamp) |
| Kotlin | Instant.now().epochSecond | Instant.ofEpochSecond(timestamp) |
Visit our code examples section for complete, copy-paste-ready implementations.
What is the Year 2038 Problem (Y2K38)?
32-bit Integer Overflow Explained
The Year 2038 Problem (Y2K38) occurs when systems using 32-bit signed integers for timestamp storage experience integer overflow on January 19, 2038, at 03:14:07 UTC. At this critical moment, the maximum timestamp value 2,147,483,647 seconds is exceeded, potentially causing system failures in legacy applications.
Max 32-bit timestamp: 2,147,483,647 = Tue Jan 19 2038 03:14:07 UTC
Solution & Status: Modern 64-bit systems use 64-bit timestamps, supporting dates until approximately 292 billion years in the future. Most current operating systems, databases, and programming languages have migrated to 64-bit timestamp handling, making Y2K38 a non-issue for newly built systems.
Unix Timestamp vs Other Formats
Key Difference: Unix timestamp (1704067200) is a compact integer requiring 4-8 bytes, while ISO 8601 (2026-01-01T00:00:00Z) is a text string requiring 19+ bytes. Unix excels in databases and APIs for instant calculations; ISO 8601 balances human readability with machine parsing.
| Aspect | Unix Timestamp | ISO 8601 |
|---|---|---|
| Format | 1704067200 | 2024-01-01T00:00:00Z |
| Timezone | Always UTC | Explicit in string |
| Storage Size | 4-8 bytes | 19+ bytes |
| Human Readable | No | Yes |
| Calculations | Simple arithmetic | Requires parsing |
| Best For | Storage, APIs, calculations | Display, logging |
Unix timestamps excel for backend processing and storage, while ISO 8601 balances human readability with machine parsing. Many systems use timestamps internally and convert to ISO 8601 for display.