Cocoa / Core Data Timestamp Converter

Most systems count time from 1 January 1970, but Apple’s frameworks use a different starting point: 1 January 2001. Timestamps from iOS and macOS databases, plist files and app exports therefore look like Unix times but convert to dates 31 years too early. This converter reads Apple timestamps in seconds or nanoseconds and converts dates back.

Apple’s reference date

Foundation’s NSDate, Swift’s Date and Core Data store time as seconds since the reference date, 1 January 2001 at 00:00:00 UTC; Apple calls this “absolute time”. The gap to the Unix epoch is exactly 978,307,200 seconds, the length of the 31 years from 1970 to 2001 including eight leap days. Adding that number to an Apple timestamp gives Unix time, which is how every conversion here works.

Seconds and nanoseconds

Core Data and most plist dates use seconds, usually with a fractional part. Since iOS 11 and macOS 10.13, some system databases, for example the Messages database, store nanoseconds since the same date instead, which produces 18-digit numbers. Choose the unit, or simply paste: a value too large to be seconds for any plausible date is read as nanoseconds automatically, and a note says so.

Mistaking it for Unix time

A Unix timestamp from recent years is a number around 1.7 to 1.8 billion, which as an Apple timestamp would be a date in the 2050s. When a value falls in that range, the converter warns that it may be a Unix timestamp, in which case the real date is 31 years earlier than shown. Negative values are valid and mean dates before 2001.

Working with Core Data databases

Core Data saves its stores as SQLite files with columns named like ZTIMESTAMP or ZCREATIONDATE. To read them in a query, add the offset and use SQLite’s date functions: datetime(ZTIMESTAMP + 978307200, 'unixepoch'). The converter shows that expression, ready to paste into the SQLite Viewer.

A worked example

The seconds value 783475200 converts to 2025-10-30T00:00:00.000Z. The nanosecond value 783475200000000000 gives the same moment, because it is the same count of seconds multiplied by a billion. In the other direction, the date 2026-10-30 00:00:00 UTC is 815011200 seconds since the reference date, and the nanosecond form is the same number followed by nine zeros.

Other epochs to know

Apple is not the only exception. Windows FILETIME counts from 1601 in 100-nanosecond steps, GPS time from 6 January 1980, and classic Mac OS used 1 January 1904, which still appears in some file formats and in Excel’s 1904 date system. When a converted date looks decades off, a different epoch is the usual explanation.

Precision

Seconds values are converted with millisecond precision, which matches JavaScript dates. Nanosecond values larger than about 9 × 10¹⁵ exceed the range JavaScript numbers represent exactly, so the last few digits are rounded; the date is correct to well under a millisecond, but do not rely on the converter to round-trip individual nanoseconds.

Related tools

• LDAP / FILETIME Converter handles Windows timestamps from 1601.
• Timestamp Converter works with ordinary Unix time.
• GPS Time Converter converts satellite week numbers.
• SQLite Viewer opens the Core Data database to query these columns.