Unix timestamp converter
Convert Unix seconds or milliseconds to UTC ISO dates and local time, or turn an ISO date with an explicit offset into a timestamp. Choose units explicitly for every conversion.
Developer Tools
Unix timestamp converter
Convert Unix seconds or milliseconds to UTC ISO dates and local time, or turn an ISO date with an explicit offset into a timestamp. Choose units explicitly for every conversion.
01Input
Use a whole integer or an ISO date with seconds and Z or ±HH:MM. Maximum 100 characters.
02Result
00:00:00
Add an input and run the conversion to see your result.
Whole seconds round down, including before 1970: 1969-12-31T23:59:59.500Z becomes −1.
02 / How to use it
About this tool
How to use this tool
Input
Choose the direction and select seconds or milliseconds. The tool does not guess the unit from the number length.
Options
Enter a whole integer or an ISO date with Z or an explicit offset. Now captures the instant when clicked.
Result
Select Convert and compare UTC with local time and its displayed zone. Copy each representation separately.
Worked example
Worked example · Unix timestamp converter
The +01:00 offset makes 01:00 the same instant as midnight UTC. Seconds since the Unix epoch are therefore zero.
Input
1970-01-01T01:00:00+01:00
Result
0 1970-01-01T00:00:00.000Z
Formats and limits
- Limits
- Use a whole integer or an ISO date with seconds and Z or ±HH:MM. Maximum 100 characters.
- Options
- Use the unit documented by the source system. One second is 1,000 milliseconds. The tool does not automatically infer the unit.
- Result
- UTC and local time represent the same instant. Local formatting uses the zone detected by your browser and its daylight saving rules.
Common issues
Are negative timestamps supported?
Yes. They represent instants before 1970-01-01T00:00:00Z, within the Date range and safe integer limits.
Which ISO format is accepted?
A real date with T, hours, minutes, seconds and Z or an explicit ±HH:MM offset. One to three fractional digits are accepted; impossible or timezone-free dates are rejected.
Review the result before using it
The +01:00 offset makes 01:00 the same instant as midnight UTC. Seconds since the Unix epoch are therefore zero.
Formats and limits
Use a whole integer or an ISO date with seconds and Z or ±HH:MM. Maximum 100 characters. Processed in this browser. No data is uploaded or saved.
Frequently Asked Questions
Which unit should I choose?
Use the unit documented by the source system. One second is 1,000 milliseconds. The tool does not automatically infer the unit.
Why does local time differ?
UTC and local time represent the same instant. Local formatting uses the zone detected by your browser and its daylight saving rules.
Are negative timestamps supported?
Yes. They represent instants before 1970-01-01T00:00:00Z, within the Date range and safe integer limits.
Which ISO format is accepted?
A real date with T, hours, minutes, seconds and Z or an explicit ±HH:MM offset. One to three fractional digits are accepted; impossible or timezone-free dates are rejected.
What happens to fractional seconds?
Whole seconds round toward negative infinity. For example, 1969-12-31T23:59:59.500Z becomes −1, not 0. Use milliseconds to preserve that precision.