24-hour clock

The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today, and is used by international standard ISO 8601. In the practice of medicine, the 24-hour clock is generally used in documentation of care as it prevents any ambiguity as to when events occurred in a patient's medical history. It is popularly referred to as military time in the United States, English-speaking Canada, Russia, and a handful of other countries where the 12-hour clock is still dominant.

Description

A time of day is written in the 24-hour notation in the form hh:mm (for example 01:23) or hh:mm:ss (for example, 01:23:45), where hh (00 to 23) is the number of full hours that have passed since midnight, mm (00 to 59) is the number of full minutes that have passed since the last full hour, and ss (00 to 59) is the number of seconds since the last full minute. In the case of a leap second, the value of ss may extend to 60. A leading zero is added for numbers under 10. This zero is optional for the hours, but very commonly used in computer applications, where many specifications require it (for example, ISO 8601).

Windows 10

Windows 10 is a personal computer operating system released by Microsoft as part of the Windows NT family of operating systems. It was officially unveiled in September 2014 following a brief demo at Build 2014. The first version of the operating system entered a public beta testing process in October 2014, leading up to its consumer release on July 29, 2015, and its release to volume licensing on August 1, 2015. To encourage the adoption of Windows 10, Microsoft announced that during its first year of availability, upgrades to the operating system would be made available free of charge to users of genuine copies of eligible editions of Windows 7, and Windows 8 after update to Windows 8.1.

Windows 10 introduces what Microsoft described as a "universal" application architecture; expanding on Metro-style apps, these apps can be designed to run across multiple Microsoft product families with nearly identical code‍—‌including PCs, tablets, smartphones, embedded systems, Xbox One, Surface Hub and HoloLens. The Windows user interface was revised to handle transitions between a mouse-oriented interface and a touchscreen-optimized interface based on available input devices‍—‌particularly on 2-in-1 PCs; both interfaces include an updated Start menu that blends elements of Windows 7's traditional Start menu with the tiles of Windows 8. The first release of Windows 10 also introduces a virtual desktop system, a window and desktop management feature called Task View, the Microsoft Edge web browser, support for fingerprint and face recognition login, new security features for enterprise environments, and DirectX 12 and WDDM 2.0 to improve the operating system's graphics capabilities for games.

Windows 7

Windows 7 (codenamed Vienna, formerly Blackcomb) is a personal computer operating system developed by Microsoft. It is a part of the Windows NT family of operating systems. Windows 7 was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009, less than three years after the release of its predecessor, Windows Vista. Windows 7's server counterpart, Windows Server 2008 R2, was released at the same time.

Windows 7 was primarily intended to be an incremental upgrade to the operating system intending to address Windows Vista's poor critical reception while maintaining hardware and software compatibility. Windows 7 continued improvements on Windows Aero (the user interface introduced in Windows Vista) with the addition of a redesigned taskbar that allows applications to be "pinned" to it, and new window management features. Other new features were added to the operating system, including libraries, the new file sharing system HomeGroup, and support for multitouch input. A new "Action Center" interface was also added to provide an overview of system security and maintenance information, and tweaks were made to the User Account Control system to make it less intrusive. Windows 7 also shipped with updated versions of several stock applications, including Internet Explorer 8, Windows Media Player, and Windows Media Center.

12-hour clock

The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods:a.m. (from the Latin ante meridiem, meaning "before midday") and p.m. (post meridiem, "after midday"). Each period consists of 12 hours numbered: 12 (acting as zero),1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11. The 24 hour/day cycle starts at 12 midnight (often indicated as 12 a.m.), runs through 12 noon (often indicated as 12 p.m.), and continues to the midnight at the end of the day.

The 12-hour clock was developed over time from the mid-second millennium BC to the 16th century AD.

History and use

The natural day/night division of a calendar day forms the fundamental basis as to why each day is split into two cycles. Originally these were one cycle which could be tracked by the position of the Sun (day) followed by one cycle which could be tracked by the Moon and stars (night). This would eventually evolve into the two 12-hour periods that started at midnight (a.m.) and noon (p.m.) which are used today. Noon itself is rarely abbreviated today, but if it is, it is denoted M.

Hour

The hour (common symbol: h or hr, h being the international form of the symbol) is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds. It is approximately ¹⁄₂₄ of a mean solar day.

An hour in the Universal Coordinated Time (UTC) time standard can include a negative or positive leap second, and may therefore have a duration of 3,599 or 3,601 seconds for adjustment purposes.

Although it is not a standard defined by the International System of Units, the hour is a unit accepted for use with SI, represented by the symbol h.

Etymology

The Middle English word ure first appears in the 13th century, as a loanword from Old French ure, ore, from Latin hōra.Hora, in turn, derives from Greek ὥρα ("season, time of day, hour"). In terms of the Proto-Indo-European language, ὥρα is a cognate of English year and is derived from the Proto-Indo-European word *i̯ēro- ("year, summer").

The ure of Middle English and the Anglo-French houre gradually supplanted the Old English nouns tīd (which survives in Modern English as tide) and stund. Stund is the progenitor of stound, which remains an archaic synonym for hour. Stund is related to the Old High German stunta (whence German Stunde, "hour, lesson"), from Germanic *stundō ("time, interval, while").