Browse Definitions:
Definition

Julian date

Contributor(s): Preston A. Larimer and Ricardo Mediavilla

1) Not to be confused with the Julian calendar, a Julian date or day number is the number of elapsed days since the beginning of a cycle of 7,980 years invented by Joseph Scaliger in 1583. The purpose of the system is to make it easy to compute an integer (whole number) difference between one calendar date and another calendar date. The 7,980 year cycle was derived by combining several traditional time cycles (solar, lunar, and a particular Roman tax cycle) for which 7,980 was a common multiple. The starting point for the first Julian cycle began on January 1, 4713 B.C. (Gregorian calendar - expressed in the ISO date format as "-4713-01-01 G") and will end on January 22, 3268 (3268-01-22 G). The following day will begin the first day of the second Julian date period (or 7,980 year cycle).

A Julian date or day number for a certain time of day on January 9, 2001, looked like this:

2451919.3423000001348555  

meaning 2,451,919 elapsed days since the beginning of the Julian cycle. The ".3423000001348555" represented the time of day ("15:12:54 EST").

It is not certain whether the Julian date or day number system was named after Joseph Scaliger's father, Julius Caesar Scaliger, or after the Julian calendar. Julian day numbers are widely used in astronomy.

2) Commonly in computer programming, Julian date has been corrupted to mean the number of elapsed days since the beginning of a particular year. For example, in this usage, the Julian date for the calendar date of 1998-02-28 would be day 59.

This was last updated in September 2005

Continue Reading About Julian date

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

  • PCAOB (Public Company Accounting Oversight Board)

    The Public Company Accounting Oversight Board (PCAOB) is a Congressionally-established nonprofit that assesses audits of public ...

  • 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 ...

SearchSecurity

  • email spam

    Email spam, or junk email, is unsolicited bulk messages sent through email with commercial, fraudulent or malicious intent.

  • distributed denial of service (DDoS) attack

    A distributed denial-of-service attack occurs when an attack originates from multiple computers or devices, usually from multiple...

  • application whitelisting

    Application whitelisting is the practice of identifying applications that have been deemed safe for execution and restricting all...

SearchHealthIT

  • athenahealth Inc.

    Based in Watertown, Mass., athenahealth Inc. is a leading vendor of cloud-based EHRs for small to medium-sized physician ...

  • Affordable Care Act (ACA or Obamacare)

    The Affordable Care Act (ACA) is legislation passed in 2010 that changed how uninsured Americans enroll in and receive healthcare...

  • HIPAA Privacy Rule

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

SearchDisasterRecovery

  • disaster recovery as a service (DRaaS)

    One approach to a strong disaster recovery plan is DRaaS, where companies offload data replication and restoration ...

  • 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 ...

SearchStorage

  • yottabyte (YB)

    A yottabyte is a measure of theoretical storage capacity and is 2 to the 80th power bytes, or, in decimal, approximately 1,000 ...

  • Kilo, mega, giga, tera, peta, exa, zetta and all that

    Kilo, mega, giga, tera, peta, exa, zetta are among the list of prefixes used to denote the quantity of something, such as a byte ...

  • brontobyte

    A brontobyte is a measure of memory or data storage that is equal to 10 to the 27th power of bytes.

SearchSolidStateStorage

  • PCIe SSD (PCIe solid-state drive)

    A PCIe SSD (PCIe solid-state drive) is a high-speed expansion card that attaches a computer to its peripherals.

  • SSD caching

    SSD caching, also known as flash caching, is the temporary storage of data on NAND flash memory chips in a solid-state drive so ...

  • NVDIMM (Non-Volatile Dual In-line Memory Module)

    An NVDIMM (non-volatile dual in-line memory module) is hybrid computer memory that retains data during a service outage.

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