Epoch Converter

What is Unix time?

Unix time (also called epoch time or POSIX time) counts the number of seconds that have elapsed since 00:00:00 UTC on January 1, 1970, ignoring leap seconds. It's the standard way most operating systems, programming languages, databases, and APIs represent a point in time internally — as a single number rather than a formatted string.

Why use a timestamp instead of a date string?

A timestamp is timezone-independent, sorts numerically, and is trivial to do arithmetic on (e.g. "is this token expired?" or "how many days between these two events?"). Formatted date strings only enter the picture when you need to display a timestamp to a human — and that's exactly what this tool converts between.

Local time isn't always one answer

Twice a year, clocks in most zones that observe daylight saving time either skip an hour or repeat one. A local time inside the skipped hour never happened, and a local time inside the repeated hour happened twice — at two different instants, an hour apart. Rather than silently guess which one you mean (or invent an instant that never occurred), this tool tells you which case you're in and, for a repeated hour, shows both instants with their own UTC offsets.

Common use cases

• Debugging API responses or database rows that store created_at as an epoch integer
• Checking a JWT's exp/iat claims (see the JWT decoder)
• Converting log timestamps to your local timezone — and, once decoded, checking what that moment was for a colleague elsewhere with the world clock and time zone converter
• Scheduling or cache-expiry calculations
• Pasting a column of timestamps from a log file or spreadsheet to convert them all at once, with a CSV you can drop straight back into a spreadsheet
• Turning a decoded timestamp into a string your code can print — the date format generator gives you the exact format string for Python, Java, C#, Go, PHP or SQL
• Deciding whether a value is really a moment in time, or a "0"/"-1"/"never expires" sentinel in disguise
• Working out what a Snowflake ID, MongoDB ObjectId, ULID or UUID v7/v1 was generated at
• Making sense of an Excel serial date, a Windows FILETIME, or a .NET Ticks value
• Computing a date range for a query — start/end of day, week, month, quarter or year, DST-aware

Why 10 digits, or 13, or 19?

A 10-digit value is almost always seconds since the epoch (Unix/Linux, most APIs, most databases). 13 digits is almost always milliseconds (JavaScript's Date.now(), many web APIs). 16 is microseconds, and 19 is nanoseconds (Go's UnixNano(), ClickHouse, InfluxDB, OpenTelemetry). Digit count is a strong prior, not a guarantee — a pre-1970 or far-future value breaks the pattern, and this tool checks the implied year rather than trusting width alone, showing every unit as a one-click alternate so you can correct it in one click if the guess is wrong. Under the hood, every unit conversion runs on BigInt rather than JavaScript's Number, which starts losing precision above 2⁵³ — so a 19-digit nanosecond value comes back exact instead of silently rounded to the nearest few hundred nanoseconds, which is what a naive Number()-based converter does.

The Year 2038 problem

Systems that store a Unix timestamp in a signed 32-bit integer (the C time_t on many older or embedded systems) run out of room at 2147483647, which is 2038-01-19T03:14:07 UTC. One second later the value overflows and wraps to a large negative number — 1901, not 2038, on an unpatched system. Nearly everything built in the last decade uses a 64-bit time_t and is unaffected, but 32-bit embedded devices, old databases and some file formats still aren't. This tool flags 2147483647 and values near −2147483648 automatically, since a value in that second range usually means "this already overflowed."

IDs that secretly carry a timestamp

Several widely-used ID formats encode the moment they were generated directly in the ID, no separate column required. A Snowflake ID (Discord, Twitter/X and several other platforms) packs milliseconds-since-a-platform-epoch into its top bits. A MongoDB ObjectId's first 4 bytes are epoch seconds. A ULID and a UUID v7 both encode 48-bit milliseconds in their first 10/12 characters — that's the whole point of the newer UUID versions, sortable-by-creation-time IDs. An older UUID v1 carries a 60-bit count of 100-nanosecond intervals since 1582. Paste any of these into the converter above and it decodes automatically.

Time math: adding, subtracting and date ranges

The Time math tab turns a resolved instant into answers you can act on: add or subtract a duration (years, months, days, hours, minutes, seconds), find the signed difference between two timestamps as both seconds and a human breakdown, and get the start/end epoch of a day, week, month, quarter or year — the pair a WHERE created_at BETWEEN start AND end query actually needs. Calendar units (years, months, days) step the wall-clock date and re-resolve in your chosen time zone, so adding "one day" across a daylight-saving change correctly comes out to 23 or 25 real hours, not a naive +86,400,000 milliseconds.

Code snippets, both directions, in real languages

The Formats & code tab prints runnable code — not a simulated result — for parsing a Unix timestamp, formatting one, and getting the current time in Python, JavaScript, Java, C#, Go, PHP, Ruby, Rust, SQL (PostgreSQL, MySQL, SQL Server, SQLite), shell, PowerShell and Excel. Every language's snippet is anchored to the same example instant, so you can copy the one you need or compare two languages line for line.

Foreign epochs

Not every system counts from 1970. Windows' FILETIME (and LDAP timestamps) count 100ns intervals from 1601. .NET's DateTime.Ticks does the same from year 1. Excel stores dates as a day count from 1899-12-30 — the number behind that "45678" a CSV import sometimes shows instead of a date. Apple's Cocoa/Core Data, classic Mac HFS+, NTP, GPS time and the astronomical Julian Day all use their own base date and unit too. The Formats & code tab converts the resolved instant into every one of these, and the Reference tab lists the base date and unit for each.