How to use this developer tool
- Select the source epoch system.
- Enter the numeric value.
- Choose whether to show all target systems.
- Review precision and reference-date notes.
#078 · Time & Date Tools Developer Tool
Epoch Converter
Convert values between Unix, Windows File Time, WebKit, Cocoa, .NET ticks, Java milliseconds, Excel serial dates, and Julian dates.
Developer Input
Time & Date ToolsAd space
What this developer tool does
The converter maps each source epoch to Unix milliseconds, then derives equivalent values for other epoch systems.
Parse source system → apply its reference-date offset and unit multiplier → normalize to Unix milliseconds → calculate target values.
Large tick and microsecond values are handled with BigInt where exact integer arithmetic is required.
Example
A Windows File Time value can be converted from 100-nanosecond ticks since 1601 to Unix time and ISO 8601.
Tips for better output
- Confirm the source epoch before conversion.
- Use BigInt for Windows File Time and .NET ticks.
- Excel's 1900 date system includes a historical leap-year compatibility issue.
FAQ
How do I convert Windows File Time to Unix time?
Subtract the 1601-to-1970 offset and convert 100-nanosecond ticks to milliseconds.
How do I convert a WebKit timestamp to a normal date?
WebKit timestamps use microseconds since 1601, so subtract the epoch offset and divide by 1000.
What is the difference between Unix time and .NET ticks?
.NET ticks use 100-nanosecond intervals since year 1, while Unix time starts in 1970.
How do I convert an Excel serial date to Unix time?
Convert days from the Excel epoch to milliseconds while accounting for the selected date system.
Why does an epoch converter show a precision warning?
The source integer may exceed JavaScript's safe Number range and require BigInt.
Related developer tools
Epoch references
| System | Reference |
|---|---|
| Unix | 1970-01-01 UTC |
| Windows / WebKit | 1601-01-01 UTC |
| .NET | 0001-01-01 UTC |