Quick answer
Unix time counts seconds since 1970-01-01 00:00:00 UTC. A timestamp of 0 is that instant, a Thursday.
Choose a direction and enter a timestamp or date. The calculator returns the UTC date and time and weekday.
Related tools: Age Calculator: Calculate your exact age in years, months and days. Time Duration Calculator: Elapsed time between two clock times, including across midnight. Hours Calculator: Hours worked between a start and end time, minus breaks.
How to use the Unix Timestamp Converter
- Choose convert: Timestamp → date and Date → timestamp.
- Optionally, enter unix timestamp (seconds) (between -8640000000000 and 8640000000000).
- Optionally, pick uTC date.
- Optionally, type uTC time (HH:MM:SS), for example 00:00:00.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Convert | Choose one: Timestamp → date; Date → timestamp | Starts at Timestamp → date |
| Unix timestamp (seconds) (optional) | A number | ≥ -8640000000000, ≤ 8640000000000 |
| UTC date (optional) | A calendar date | — |
| UTC time (HH:MM:SS) (optional) | Text, such as 00:00:00 | — |
Formula and method
Formula
Unix time = seconds since 1970-01-01 00:00:00 UTC
IEEE-754 double precision; shown to the decimals indicated.
Leap seconds are ignored, as in POSIX time. The date mode uses UTC.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Convert = Timestamp → date; Unix timestamp (seconds) = 0.
| Result | Value |
|---|---|
| UTC date and time | 1970-01-01 00:00:00 UTC |
| Weekday | Thursday |
Example 2
Inputs: Convert = Timestamp → date; Unix timestamp (seconds) = 1700000000.
| Result | Value |
|---|---|
| UTC date and time | 2023-11-14 22:13:20 UTC |
| Weekday | Tuesday |
Example 3
Inputs: Convert = Timestamp → date; Unix timestamp (seconds) = 31536000.
| Result | Value |
|---|---|
| UTC date and time | 1971-01-01 00:00:00 UTC |
| Weekday | Friday |
The first line is the headline result (uTC date and time). Below it the unix Timestamp Converter lists weekday, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Worked example
86,400 is one day, so 86,400 is 1970-01-02. A timestamp of 1,700,000,000 is 14 November 2023.
Where this estimate stops applying
Whole seconds only; many systems use milliseconds, which need dividing by 1,000. Signed 32-bit timestamps overflow in January 2038.
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Unix timestamp (seconds): left empty shows "Enter a timestamp." beside that field and no result.
- UTC date: left empty shows "Enter a date." beside that field and no result.
Choosing between the Unix Timestamp Converter and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Age Calculator](/time/age-calculator/) | date of birth | Your age |
| [Time Duration Calculator](/time/time-duration-calculator/) | start time and end time | Duration |
| [Hours Calculator](/time/hours-calculator/) | start time and end time | Hours worked |
| [Period Calculator](/time/period-calculator/) | first day of last period, average cycle length and period length | Next period starts |
| [Time Card Calculator](/time/time-card-calculator/) | start times, end times and unpaid break per day | Total time |
Background: dates and times
Date and time results depend on the conventions a tool uses: whether the end date counts, whether weekends and holidays are skipped, how months of different lengths are handled and whether time zones are applied. This page states its convention, and the worked examples show it.
Dates use the Gregorian calendar and calendar days unless the page says otherwise; check deadlines against the rule in your contract or regulation.
Assumptions and limitations
- Whole seconds only
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for unix timestamp (seconds) and uTC date to confirm this.
Frequently asked questions
What is the Year 2038 problem?
A 32-bit overflow on 19 January 2038.
Is it affected by time zones?
No, it is always UTC.
How do I get milliseconds?
Multiply seconds by 1,000 for the millisecond timestamps used by JavaScript and many APIs.
What does the Unix Timestamp Converter calculate?
Convert between Unix timestamps (seconds) and UTC dates. It returns UTC date and time and Weekday.
What formula does the Unix Timestamp Converter use?
Unix time = seconds since 1970-01-01 00:00:00 UTC. Leap seconds are ignored, as in POSIX time.
What do I need to enter in the unix Timestamp Converter?
You enter Convert. Optional: Unix timestamp (seconds), UTC date and UTC time (HH:MM:SS).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Whole seconds only.
What does the “Convert” option change?
It sets how the unix Timestamp is worked out. The choices are Timestamp → date and Date → timestamp.
What is an example of a unix Timestamp result?
With convert Timestamp → date and unix timestamp (seconds) 0, the uTC date and time is 1970-01-01 00:00:00 UTC.
Where does the method come from?
The method follows: POSIX.1 (IEEE Std 1003.1) definition of seconds since the Epoch.
Related calculators
- Age Calculator — Calculate your exact age in years, months and days.
- Time Duration Calculator — Elapsed time between two clock times, including across midnight.
- Hours Calculator — Hours worked between a start and end time, minus breaks.
- Period Calculator — Predicted next period, ovulation and fertile window from your last period.
- Time Card Calculator — Total hours, overtime and gross pay from daily start and end times.
- Time From Now Calculator — Clock time after adding or subtracting minutes.
Sources
- POSIX.1 (IEEE Std 1003.1) definition of seconds since the Epoch
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.