---
title: Time Utilities
framework: corefoundation
role: collectionGroup
role_heading: API Collection
path: corefoundation/time-utilities
---

# Time Utilities

## Overview

Overview Core Foundation measures time in units of seconds. The base data type is the CFTimeInterval, which measures the difference in seconds between two times. Fixed times, or dates, are defined by the CFAbsoluteTime data type, which measures the time interval between a particular date and the absolute reference date of Jan 1 2001 00:00:00 GMT. The CFGregorianDate structure represents absolute times in terms of the Gregorian calendar. Functions such as CFAbsoluteTimeGetGregorianDate(_:_:) use a CFTimeZone object to obtain the local time in a particular time zone. The CFDate opaque type wraps an absolute time into a CFTypeRef-base object, allowing you to put time objects into collections and property lists and to be handled by other object-oriented parts of Core Foundation.

## Topics

### Core Foundation Time Utilities Miscellaneous Functions

- [CFAbsoluteTimeAddGregorianUnits(_:_:_:)](corefoundation/cfabsolutetimeaddgregorianunits(_:_:_:).md)
- [CFAbsoluteTimeGetCurrent()](corefoundation/cfabsolutetimegetcurrent().md)
- [CFAbsoluteTimeGetDayOfWeek(_:_:)](corefoundation/cfabsolutetimegetdayofweek(_:_:).md)
- [CFAbsoluteTimeGetDayOfYear(_:_:)](corefoundation/cfabsolutetimegetdayofyear(_:_:).md)
- [CFAbsoluteTimeGetDifferenceAsGregorianUnits(_:_:_:_:)](corefoundation/cfabsolutetimegetdifferenceasgregorianunits(_:_:_:_:).md)
- [CFAbsoluteTimeGetGregorianDate(_:_:)](corefoundation/cfabsolutetimegetgregoriandate(_:_:).md)
- [CFAbsoluteTimeGetWeekOfYear(_:_:)](corefoundation/cfabsolutetimegetweekofyear(_:_:).md)
- [CFGregorianDateGetAbsoluteTime(_:_:)](corefoundation/cfgregoriandategetabsolutetime(_:_:).md)
- [CFGregorianDateIsValid(_:_:)](corefoundation/cfgregoriandateisvalid(_:_:).md)

### Data Types

- [CFAbsoluteTime](corefoundation/cfabsolutetime.md)
- [CFGregorianDate](corefoundation/cfgregoriandate.md)
- [CFGregorianUnits](corefoundation/cfgregorianunits.md)
- [CFTimeInterval](corefoundation/cftimeinterval.md)

### Constants

- [CFGregorianUnitFlags](corefoundation/cfgregorianunitflags.md)
- [Predefined Time Interval Values](corefoundation/predefined-time-interval-values.md)

## See Also

### Related Documentation

- [Date and Time Programming Guide for Core Foundation](apple-archive/documentation/CoreFoundation/Conceptual/CFDatesAndTimes.md)

### Utilities

- [Base Utilities](corefoundation/base-utilities.md)
- [Byte-Order Utilities](corefoundation/byte-order-utilities.md)
- [Core Foundation URL Access Utilities](corefoundation/core-foundation-url-access-utilities.md)
- [Preferences Utilities](corefoundation/preferences-utilities.md)
- [Socket Name Server Utilities](corefoundation/socket-name-server-utilities.md)