A Mac Absolute Time / CFAbsoluteTime value counts seconds from 2001-01-01T00:00:00Z. Its source epoch and unit need to travel with it; the number alone cannot tell you which clock it belongs to.
Conversion rule
Unix seconds = Mac Absolute Time + 978307200
The converter applies that relationship and returns Unix seconds, epoch milliseconds, ISO 8601 UTC, and a readable UTC value. Keep the original value as well when investigating a log or export so the conversion can be checked later.
Where mistakes happen
Apple timestamps often look like ordinary seconds but use a 2001 epoch. Do not feed them directly to a Unix converter without the offset.
A safer workflow
- Identify the platform and field name before doing arithmetic.
- Preserve the original value as a string when it may exceed JavaScript safe-integer precision.
- Convert once at the boundary, then store or compare a declared Unix unit.
- Format in a named timezone only when presenting the resulting instant to a person.
Related format converters
Frequent questions:
- Q: What is the CFAbsoluteTime epoch?
- A: CFAbsoluteTime counts seconds since January 1, 2001 00:00:00 UTC, the Core Foundation/Cocoa reference date.
- Q: How do I convert Mac absolute time to Unix time?
- A: Add 978,307,200 seconds to the Mac absolute time to get a Unix timestamp in seconds.
- Q: Is Mac absolute time the same as Core Data timestamps?
- A: Yes. Core Data stores dates as CFAbsoluteTime (seconds since 2001), so the conversion is identical.