Browse Definitions:
Definition

hour (hr)

The hour (symbolized hr) is a unit of time , equivalent to 3600 second s (s), 60 minute s (min), or 1/24 of a mean solar day (msd). The hour is also used by astronomers as one of two coordinates that define the positions of objects in the sky.

Informally, time is measured according to a scheme that uses two 12-hr segments per mean solar day. The first segment, a.m., begins at midnight and ends at noon. The second segment, p.m., begins at noon and ends at midnight. Time in this format is written in the form h:mm or hh:mm, where h or hh represents the hour from 1 to 12, and mm represents the minute from 00 to 59.

Astronomers, most engineers, aviators, navigators, and military people use a 24-hour time scheme that begins and ends at midnight. In this format, time is denoted in the form hhmm, where hh represents the hour from 00 to 23, and mm represents the minute from 00 to 59.

In celestial coordinates, the hour (hr) is the standard unit of right ascension (RA). Right ascension is measured from west to east along the celestial equator, an imaginary line in the heavens that lies directly over Earth's geographic equator. There are 24 hr of right ascension in a complete circle; therefore 1 hr is the equivalent of 15 angular degree s (15° or 15 deg). The point RA = 0 is the vernal equinox, the position of the Sun in the heavens as it crosses the celestial equator going from south to north. This occurs annually on March 20 or 21.

Also see time , second , angular degree , International System of Units ( SI ), and Table of Physical Units .

This was last updated in March 2011

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

Powered by:

SearchCompliance

  • cyborg anthropologist

    A cyborg anthropologist is an individual who studies the interaction between humans and technology, observing how technology can ...

  • RegTech

    RegTech, or regulatory technology, is a term used to describe technology that is used to help streamline the process of ...

  • conduct risk

    Conduct risk is the prospect of financial loss to an organization that is caused by the actions of an organization's ...

SearchSecurity

  • security

    Security, in information technology (IT), is the defense of digital information and IT assets against internal and external, ...

  • insider threat

    An insider threat is a malicious hacker (also called a cracker or a black hat) who is an employee or officer of a business, ...

  • virus (computer virus)

    A computer virus is malicious code that replicates by copying itself to another program, computer boot sector or document.

SearchHealthIT

  • HIPAA Privacy Rule

    The Standards for Privacy of Individually Identifiable Health Information, commonly known as the HIPAA Privacy Rule, establishes ...

  • HIPAA business associate agreement (BAA)

    Under the U.S. Health Insurance Portability and Accountability Act of 1996, a HIPAA business associate agreement (BAA) is a ...

  • telemedicine

    Telemedicine is the remote delivery of healthcare services, such as health assessments or consultations, over the ...

SearchDisasterRecovery

  • data recovery

    Data recovery restores data that has been lost, accidentally deleted, corrupted or made inaccessible. Learn how data recovery ...

  • disaster recovery plan (DRP)

    A company's disaster recovery policy is enhanced with a documented DR plan that formulates strategies, and outlines preparation ...

  • fault-tolerant

    Systems with integrated fault tolerance are designed to withstand multiple hardware failures to ensure continuous availability.

SearchStorage

  • Secure Digital card (SD card)

    SD cards use flash memory to provide nonvolatile storage. They are more rugged than traditional storage media and are used in ...

  • data storage

    In a computer, storage is the place where data is held in an electromagnetic or optical form for access by a computer processor.

  • flash storage

    Flash-based storage, based on flash memory, is used for data repositories, storage systems and consumer devices, such as USB ...

SearchSolidStateStorage

  • flash file system

    Flash file systems are designed specifically for memory devices. A well-designed flash device and flash file system ensure ...

  • IOPS (input/output operations per second)

    IOPS measures the maximum number of reads and writes to non-contiguous storage. It is not an actual benchmark since vendor ...

  • eMMC (embedded MultiMediaCard)

    An embedded MultiMediaCard (eMMC) is a small storage device made up of NAND flash memory and a simple storage controller.

SearchCloudStorage

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

  • Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA ...

Close