What Is Epoch Time Zero? January 1 1970 Explained

Epoch time zero is January 1 1970 at 00:00:00 UTC — the fixed starting point that all computers use to measure time. Every Unix timestamp is a count of seconds that have elapsed since this moment. Use the Unix Timestamp Converter to convert any date to its epoch time value or back to a human-readable date instantly.

Epoch time zero is the universally agreed reference point — also called the Unix epoch or POSIX time zero — from which every computer timestamp is calculated as a positive or negative integer.

What Is Epoch Time Zero?

Epoch time zero — also known as the Unix epoch, POSIX time zero, or simply epoch 0 — is the exact moment in time defined as January 1 1970 at 00:00:00 UTC. It is the fixed zero point from which all Unix timestamps are counted.

Every timestamp in the Unix system represents the total number of seconds that have passed since this moment. The number 0 in epoch time is exactly midnight UTC on January 1 1970. Every second after that adds 1 to the count. Every second before it subtracts 1.

A Unix timestamp is a single integer counting the number of seconds elapsed since January 1 1970 at 00:00:00 UTC — with no time zone, no slashes, and no AM/PM attached.

The epoch system has 4 key properties that made it the universal standard for computer timekeeping — it is exact (capable of millisecond precision), simple (a single integer any computer can store), universal (the same value everywhere on Earth simultaneously), and sortable (larger numbers always mean later times).

Why Did Unix Time Start on January 1 1970?

There is nothing magical about the date. When the Unix operating system was being built at Bell Labs in the late 1960s and early 1970s, its designers needed a fixed reference point to count from — a clean, round, recent date that every system could agree on.

January 1 1970 was chosen for 3 practical reasons:

It was the start of a new decade. A round number at the boundary of the 1970s was easy to remember and easy to verify manually when debugging timestamps in early systems.

It aligned with the widespread introduction of UTC. The international adoption of Coordinated Universal Time as the global standard was underway in the late 1960s — anchoring Unix time to a recent UTC date made the two systems naturally compatible.

It kept time math manageable. Early Unix systems originally used January 1 1971 as the epoch — but the date was shifted back one year to 1970 to make calendar arithmetic easier and to leave more room for future timestamps without hitting storage limits too quickly.

The result was a convenient, round number that engineers at Bell Labs could all agree on as a fixed zero — and it has been the universal foundation for computer timekeeping ever since. Every Unix-descended system — Linux, macOS, Android, iOS, and the servers behind most websites — has counted from that same instant for over 50 years.

How Does Epoch Time Zero Work in Practice?

The epoch system counts forward and backward from January 1 1970:

• The value 0 represents exactly January 1 1970 at 00:00:00 UTC
• Positive numbers represent dates after January 1 1970 — for example 1780000000 translates to approximately May 2026
• Negative numbers represent dates before January 1 1970 — for example -86400 represents exactly one day prior — December 31 1969

Milestone timestamps — here are key moments in Unix time history expressed as epoch values:

What Is the Difference Between Seconds and Milliseconds in Epoch Time?

Two units are in everyday use for epoch time — and confusing them is the single most common timestamp error:

Seconds — a 10-digit number today (for example 1780000000). Used by databases, spreadsheets, command-line tools, most back-end code, and Discord timestamp tags.

Milliseconds — a 13-digit number, exactly 1000 times bigger (for example 1780000000000). This is what JavaScript Date.now() and most web APIs return by default.

If a converter gives back a date in the year 54000 or returns a date back in 1970, you almost certainly fed it the wrong unit. The fix is a single step — divide milliseconds by 1000 to get seconds, or multiply the other way. You can verify any value instantly with the Unix Timestamp Converter.

Is Epoch Time Always UTC?

Yes — a Unix timestamp has no time zone baked into it. It is always fixed to UTC, the world's reference clock. The same number 1780000000 represents the identical instant everywhere on Earth simultaneously — but displays as a different local time in each timezone.

For example the value 1780000000 is:

• 22:13:20 in London (UTC)
• 17:13:20 in New York (UTC-5)
• 08:13:20 the following morning in Sydney (UTC+10)

The epoch number itself never changes — only the wall-clock label changes when each region applies its own UTC offset. This is the core appeal of Unix time — store one neutral number and let every device translate it to local time when it displays it to a person. This is exactly how Discord timestamps work — the raw epoch number is stored once and each user's client converts it to their own local timezone automatically.

How Does Epoch Time Relate to Discord Timestamps?

Discord timestamps are built directly on Unix epoch time. When you create a Discord timestamp tag, you supply a 10-digit Unix timestamp in seconds since January 1 1970 — and Discord converts it to each viewer's local timezone automatically.

Discord also uses a modified epoch for its internal Snowflake ID system. Instead of counting from January 1 1970, Discord's Snowflake IDs count milliseconds from January 1 2015 — a custom Discord epoch constant of 1420070400000 milliseconds. This extends the useful lifespan of Discord's 64-bit ID system until approximately the year 2084.

Use the Discord Timestamp Generator to convert any date to a Discord timestamp tag, or use the Discord Snowflake ID Decoder to extract the creation date from any Discord ID using the epoch formula.

What Is the Year 2038 Problem?

For decades many systems stored Unix timestamps as signed 32-bit integers. A 32-bit signed integer can only count as high as 2,147,483,647 — and the Unix clock reaches exactly that value at 03:14:07 UTC on January 19 2038. One second later the counter overflows and wraps around to a large negative number which reads back as a date in October 1901.

This is the Year 2038 problem — the computer equivalent of the Y2K bug, but for time storage rather than year display.

The fix is already widespread — modern systems use 64-bit integers for timestamp storage, which raises the limit to roughly 292 billion years from now. Most current phones, servers, and operating systems are already 64-bit clean. The lingering risk is in old embedded hardware — industrial controllers, legacy medical devices, and similar systems that have never been updated and still use 32-bit time storage.

How Is Epoch Time Used in Programming and Databases?

Unix epoch time is the universal standard for time storage in software for 5 practical reasons:

Space efficiency — storing a timestamp as an integer takes 4 to 8 bytes. Storing the equivalent formatted date string takes 20 or more bytes. At billions of rows this difference matters significantly.

Indexing performance — integer fields index and search faster than string or date fields in every major database engine. This is especially important when millions of rows contain timestamps.

Cross-platform compatibility — a Unix timestamp works identically across every programming language and operating system. No conversion needed when moving data between systems.

Mathematical operations — calculating the difference between two moments is a simple subtraction. Adding a duration is simple addition. No calendar library needed for basic time math.

Timezone independence — a single Unix timestamp can be converted to any timezone on display without storing additional data. The stored value is always UTC-anchored.

What Do Different Systems Use as Their Epoch Zero?

Not every system uses January 1 1970 as its epoch zero — different platforms chose different reference points:

When converting between systems, always check which epoch the source system uses — using the wrong epoch constant produces dates that are off by decades.

Common Mistakes to Avoid

• Confusing seconds and milliseconds. A 10-digit number is seconds — a 13-digit number is milliseconds. Using milliseconds where seconds are expected produces dates thousands of years in the future. Always divide by 1000 when converting from milliseconds to seconds.
• Assuming epoch time has a timezone. Unix timestamps are always UTC-anchored — they have no timezone baked in. Apply the timezone offset only at the display layer, never at the storage layer.
• Using 32-bit storage for new systems. Any system built today that stores Unix timestamps as 32-bit integers will fail in 2038. Always use 64-bit integer storage.
• Forgetting negative timestamps exist. Dates before January 1 1970 have negative Unix timestamps. Not all systems handle negative values correctly — test explicitly if your application needs to represent pre-1970 dates.
• Mixing up different epoch constants. Discord's internal epoch is 1420070400000 (January 1 2015 in milliseconds) — not 0. Using the wrong epoch constant when decoding Discord Snowflake IDs produces dates in 1970 instead of the correct creation date.

Related Guides

• What Is a Unix Timestamp?
• Unix Time vs UTC — What Is the Difference?
• Epoch vs Unix Time — What Is the Difference?
• How Discord Timestamps Use Unix Time Under the Hood

Convert any date to a Unix timestamp instantly with the Unix Timestamp Converter, generate a Discord timestamp tag with the Discord Timestamp Generator, or decode any Discord Snowflake ID with the Discord Snowflake ID Decoder.