Question: Up to how far off can the Deal Timeball be from Coordinated Universal Time?
Context: Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London.  GMT was formerly used as the international civil time standard, now superseded in that function by Coordinated Universal Time (UTC).  Today GMT is considered equivalent to UTC for UK civil purposes (but this is not formalised) and for navigation is considered equivalent to UT1 (the modern form of mean solar time at 0° longitude); these two meanings can differ by up to 0.9 s. Consequently, the term GMT should not be used for precise purposes. Fractional lambda switching (FλS) leverages on time-driven switching (TDS) to realize sub-lambda switching in highly scalable dynamic optical networking, which requires minimum (possibly optical) buffers.  Fractional lambda switching implies switching fractions of optical channels as opposed to whole lambda switching where whole optical channels are the switching unit.  In this context, TDS has the same general objectives as optical burst switching and optical packet switching: realizing all-optical networks with high wavelength utilization.  TDS operation is based on time frames (TFs) that can be viewed as virtual containers for multiple IP packets that are switched at every TDS switch based on and coordinated by the UTC (coordinated universal time) signal implementing pipeline forwarding.  In the context of optical networks, synchronous virtual pipes SVPs typical of pipeline forwarding are called fractional lambda pipes (FλPs). In modern usage, civil time refers to statutory time scales designated by civilian authorities, or to local time indicated by clocks.  Modern civil time is generally standard time in a time zone at a fixed offset from Coordinated Universal Time (UTC) or from Greenwich Mean Time (GMT), possibly adjusted by daylight saving time during part of the year.  UTC is calculated by reference to atomic clocks, and was adopted in 1972.  Older systems use telescope observations. The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time (UTC) when standard time is in effect, and by subtracting six hours during daylight saving time (UTC−6).  The clock time in this zone is based on the mean solar time at the 105th meridian west of the Greenwich Observatory.  In the United States, the exact specification for the location of time zones and the dividing lines between zones is set forth in the Code of Federal Regulations at 49 CFR 71. Malaysia Standard Time (MST; Malay: "Waktu Piawai Malaysia" , WPM ) or Malaysia Time (MYT) is a standard time used in Malaysia.  It is 8 hours ahead of Greenwich Mean Time and Coordinated Universal Time.  The local mean time in Kuala Lumpur was originally .  Peninsular Malaysia used this local mean time until 1880, when they changed to Singapore mean time .  Between the end of the Second World War and the formation of Malaysia on 16 September 1963, it was known as British Malayan Standard Time, which was hours ahead of Greenwich Mean Time.  At 2330 hrs local time of 31 December 1981, people in Peninsular Malaysia adjusted their clocks and watches ahead by 30 minutes to become 00:00 hours local time of 1 January 1982, to match the time in use in East Malaysia, which is .  SGT (Singapore) as follow on the same until now. Deal Timeball is a Victorian maritime Greenwich Mean Time signal located on the roof of a waterfront four-storey tower in the coastal town of Deal, in Kent, England.  It was established in 1855 by the Astronomer Royal George Biddell Airy in collaboration with Charles V. Walker, superintendent of telegraphs for the South Eastern Railway Company.  It was built by the Lambeth firm of engineers Maudslay and Field.  The time ball, which, like the Greenwich time ball, fell at 1 pm precisely, was triggered by an electric signal directly from the Royal Observatory. The time correction DUT1 (sometimes also written DUT) is the difference between Universal Time (UT1), which is defined by Earth's rotation, and Coordinated Universal Time (UTC), which is defined by a network of precision atomic clocks. A day is a unit of time.  In common usage, it is either an interval equal to 24 hours or daytime, the consecutive period of time during which the Sun is above the horizon.  The period of time during which the Earth completes one rotation with respect to the Sun is called a "solar day".  Several definitions of this universal human concept are used according to context, need and convenience.  In 1960, the second was redefined in terms of the orbital motion of the Earth, and was designated the SI base unit of time.  The unit of measurement "day", redefined in 1960 as 86 400 SI seconds and symbolized "d", is not an SI unit, but is accepted for use with SI.  A civil day is usually 86 400 seconds, plus or minus a possible leap second in Coordinated Universal Time (UTC), and occasionally plus or minus an hour in those locations that change from or to daylight saving time.  The word "day" may also refer to a day of the week or to a calendar date, as in answer to the question, "On which day?"  The life patterns of humans and many other species are related to Earth's solar day and the day-night cycle (see circadian rhythms). Universal Time (UT) is a time standard based on Earth's rotation.  It is a modern continuation of Greenwich Mean Time (GMT), i.e., the mean solar time on the Prime Meridian at Greenwich, London, UK.  In fact, the expression "Universal Time" is ambiguous (when accuracy of better than a few seconds is required), as there are several versions of it, the most commonly used being Coordinated Universal Time (UTC) and UT1 (see below).  All of these versions of UT, except for UTC, are based on Earth's rotation relative to distant celestial objects (stars and quasars), but with a scaling factor and other adjustments to make them closer to solar time.  UTC is based on International Atomic Time, with leap seconds added to keep it within 0.9 second of UT1. Central European Time (CET), used in most parts of Europe and a few North African countries, is a standard time which is 1 hour ahead of Coordinated Universal Time (UTC).  The time offset from UTC can be written as .  The same standard time, , is also known as Middle European Time (MET, German: ) and under other names like Berlin Time, Romance Standard Time (RST), Paris Time or Rome Time.
Answer: 0.9 s.