What is CFAbsoluteTime?

CFAbsoluteTime is an Apple Core Foundation type measuring seconds since the reference date of midnight on 1 January 2001 in UTC. It underlies NSDate and Date in Cocoa and appears in many macOS and iOS data formats.

How does it relate to Unix time?

The Apple reference date is 978,307,200 seconds after the Unix epoch of 1 January 1970. The tool adds that offset to convert CFAbsoluteTime to a Unix timestamp and a normal date.

Why do I sometimes see negative values?

A CFAbsoluteTime before the 2001 reference date is negative, since it counts backwards from the origin. The tool handles negative values and dates before 2001 correctly.

Where will I encounter CFAbsoluteTime?

It shows up in macOS and iOS plists, Safari and WebKit history and cache files, Spotlight metadata, and other Apple artifacts, which is why forensic and debugging work often needs to decode it.

Are fractional seconds supported?

Yes. CFAbsoluteTime is a floating-point value, so fractional seconds are allowed on input and preserved when converting from a date that carries sub-second precision.

Mac Absolute Time Converter

What CFAbsoluteTime is

Apple’s Core Foundation measures time as CFAbsoluteTime, a floating-point count of seconds from a single reference instant: midnight on 1 January 2001 in UTC. This is the basis of NSDate and Swift’s Date, so the same value turns up throughout macOS and iOS. Because the origin differs from the familiar Unix epoch, the raw numbers are easy to misread; this tool converts them to ordinary dates and back.

How it works

The whole conversion rests on one offset. The Apple reference date of 1 January 2001 is exactly 978,307,200 seconds after the Unix epoch of 1 January 1970. To turn a CFAbsoluteTime into a date the tool adds that offset to get a Unix timestamp, then builds a UTC date from it. Going the other way it computes the Unix seconds for the date and subtracts the offset.

662688000   ->  2022-01-01T00:00:00Z
0           ->  2001-01-01T00:00:00Z
2022-01-01T00:00:00Z  ->  662688000

Example and notes

CFAbsoluteTime is defined in UTC, so the tool reads and writes UTC; convert local times before entering them. Values are floating point, so fractional seconds are allowed, and values before the 2001 reference date are simply negative. The result also shows the matching Unix timestamp, which makes it straightforward to line up Apple artifacts with logs and databases that use Unix time.