Which Years Have the Same Calendar?

Reuse your yearly calendar by finding years that have the same number of days and start on the same day of the week.

Repeats every 6, 11, or 12 years

A staffer at the USA’s National Institute of Standards and Technology (NIST) tried to disable backup generators powering some of its Network Time Protocol infrastructure, after a power outage around Boulder, Colorado, led to errors.

As explained in a mailing list post by Jeffrey Sherman, a NIST supervisory physicist who maintains the institute’s atomic clocks, “The atomic ensemble time scale at our Boulder campus has failed due to a prolonged utility power outage.”

Sherman, whose LinkedIn bio proclaims he is “One of the few federal employee actually paid to watch the clocks all day,” says one impact of the incident “is that the Boulder Internet Time Services no longer have an accurate time reference.”

That’s bad because one of the things NIST uses its atomic clocks for is to provide a Network Time Protocol service, the authoritative source of timing information that the computing world relies on so that diverse systems can synchronize events. If NTP isn’t working, outcomes can include difficulties authenticating between systems, meaning applications can become unstable.

At this point, readers might wonder why NIST can’t just turn off the inaccurate service. Sherman said a backup generator kicked in and kept the servers running.

“I will attempt to disable them [the generators] to avoid disseminating incorrect time,” he wrote.

TL;DR: If you want to operate a secure environment you should use your own on-site stratum 1 NTP servers along with authentication. This is the only way to eliminate time spoofing attacks from the outside. Don’t reduce your overall security to a stateless and unauthenticated (read: easy-to-spoof) network protocol!

If you are using a couple of different NTP sources it might be not that easy for an attacker to spoof your time – though not unfeasible at all. And think about small routers with VPN endpoints and DNSSEC resolving enabled, or IoT devices such as cameras or door openers – they don’t even have a real-time clock with a battery inside. They fully rely on NTP.

This is what this blogpost series is all about. Let’s dig into it. ;)

10 states across the country have enacted legislation to permanently observe daylight saving time. They are Maine, Florida, Alabama, Georgia, Louisiana, Tennessee, Delaware, Colorado, Texas, and Wyoming.

However, they need congressional approval to begin observing that change.

According to The Hill, “states do have the ability to lock their clocks, current federal regulations limit their decision to year-round standard time only.”

Arizona and Hawaii are currently the only two states that observe year-round standard time.

California voters approved a measure to do away with daylight saving time in 2018, but it has not yet come into effect.

Americans are split on the issue, but support for scrapping daylight saving time is growing, meaning people prefer more light in the morning and less in the evening. //

Poll found 54% of Americans are ready to do away with the practice.

Meanwhile, just 40% say they are in favor of observing daylight saving time — the lowest level in recorded history.

Alan J. Wylie

VMS got it right

VMS (since 1977) has stored time as 100ns clock ticks since 17 November 1858 (the start of the Reduced Julian Day (an astronomical timescale, the "reduced" variant was introduced by the Smithsonian Astrophysical Observatory in 1957 to record the orbit of Sputnik). It will run out of bits in the year 31,086.

Evil Auditor

Re: VMS got it right
...and about 29,000 years from now, someone will have discovered an ancient calculation machine and will have figured out how it worked. And they will see that its clock stops in the year 31,086. And some of them will start a cult that believes the end is near for an ancient civilisation allowed their calender to run until then...

Phil O'SophicalSilver badge

Re: VMS got it right

VMS got most things right.

There is, though, a well-known bug filed against VMS for a related issue. The standard message display only permits 4-digit years, so even if the clock is fine until 31,086 there will be a display error when it ticks over on Dec 31st 9999. Last time I saw that bug in the DEC tracking system it was in an 'accepted' state, with a note that it will be fixed "in a future major architecture". Sadly unlikely now...

vtcodger

Re: Attitude problem
YOU may have spent New Years Eve 2000 at a great party. I and many others I'm sure, spent New Years morning,2000 booting 100-plus PCs to make sure they at least sort of worked -- never a certainty with Windows-98 even on normal mornings.

MiguelC

Re: Attitude problem
I was on duty that evening. At midnight we nodded, saluted each other, and went to work checking everything was running smoothly. Having had no alerts whatsoever, at around 1AM I went to the nearest ATM and checked my balance and latest account movements (an account in another bank than the one I was working for at the time). There was an interest credit of around the equivalent of 3000€. Resisting the urge to spend it there and then, I went back, showed the slip to my co-workers and pondered on what would happen from there on. At 8 AM, after an uneventful night on the job, I went down and checked my balance again. Without a trace of that earlier payment, it now showed the correct and, unfortunately, much smaller interest deposit...

Someone's night was indeed a lot more eventful than mine ;) //

Bill GraySilver badge
Reply Icon
Re: The bug is in the support library code (libc?) of a 1982 C compiler?

I suspect most time library code of this vintage also omits the year 2000 leap year (as I recall SGI Indigo Irix 4 did) and would be a day out after 2000.02.28.

I dunno how common that particular error would be? To screw things up that way, you have to simultaneously know that (in the Gregorian calendar) "century" years are not leap years, but also not know that years evenly divisible by 400 are leap years. That is to say, you have to be a little ignorant, but not completely ignorant.

If you're completely ignorant of the problem, you'll say that 2000 should have a leap day, and be correct for the wrong reasons.

Museum boffins find code that crashes in 2037

A stark warning about the upcoming Epochalypse, also known as the "Year 2038 problem," has come from the past, as National Museum Of Computing system restorers have discovered an unsetting issue while working on ancient systems.

Robin Downs, a volunteer who was recently involved in an exhibition of Digital Equipment Corporation (DEC) gear at the museum, was on hand to demonstrate the problem to The Register in the museum's Large Systems Gallery, which now houses a running PDP-11/73. //

"So we found bugs that exist, pre-2038, in writing this that we didn't know about."

The Year 2038 problem occurs in systems that store Unix time – the number of seconds since the Unix epoch (00:00:00 UTC on January 1, 1970) in a signed 32-bit integer (64-bit is one modern approach, but legacy systems have a habit of lingering).

At 03:14:07 UTC on January 19, 2038, the second counter will overflow. In theory, this will result in a time and date being returned before the epoch – 20:45:52 UTC on December 13, 1901, but that didn't happen for Downs. //

zb42
As the article is specifically about date problems that occur before the 32bit unix time rollover, I think it should be mentioned that:

32bit NTP is going to roll over on the 7th of February 2036.

Sunrise, sunset, moon phase

Earth is expected to spin more quickly in the coming weeks, making some of our days unusually short. On July 9, July 22 and Aug. 5, the position of the moon is expected to affect Earth's rotation so that each day is between 1.3 and 1.51 milliseconds shorter than normal.

The big internet corporations (like Google, Meta, Amazon) have independently developed their own smearing behavior, some even iterated over multiple smearing patterns. If you search for <corporation> leap smear with an internet search engine of your choice, you will find blog posts and documentation where they explain their respective approach. I suggest you research this for any upstream server you intend to use. A quick summary of the ones I came up with spontaneously:

• Google, Amazon: Smeared from noon to noon around the leap with 1/86400 of a second added to each second
• Meta: Smeared from the leap until 17 hours later in a non-linear curve
• Cloudflare: Standard-compliant insertion/deletion of a leap second and propagation of the leap indicator (that’s why they are allowed in the pool)
• Microsoft: No idea what software their time servers are running, but the Windows Time Service included in Windows machines does not handle leap seconds and just resyncs after one happens

All of this is best practice information and much less relevant since the decision was made to do away with leap seconds in the foreseeable future. //

Apple also offers good collection of stratum 1 servers that doesn’t use leap second smearing. Someone compiled a (non-definitive) list of them so you can see if they are worth using for your location:

pool time.apple.com

Every year, millions of people endure the biannual stupidity of Daylight Saving Time (DST), and we have a handful of historical geniuses to thank for this life-ruining ritual. Sure, they thought they were solving big problems, but instead, they handed future generations a headache disguised as innovation. Benjamin Franklin joked about saving candles by waking up earlier, and people were dumb enough to run with it. Yes, folks, this is why satire needs a disclaimer: Franklin was trolling, but the world took him seriously. And here we are, centuries later, living his joke as reality.

The Prime Meridian is the universally decided zero longitude, an imaginary north/south line which bisects the world into two and begins the universal day. The line starts at the north pole, passes across the Royal Observatory in Greenwich, England, and ends at the south pole. Its existence is purely abstract, but it is a globally-unifying line that makes the measurement of time (clocks) and space (maps) consistent across our planet.

The Greenwich line was established in 1884 at the International Meridian Conference, held in Washington DC. That conference's main resolutions were: there was to be a single meridian; it was to cross at Greenwich; there was to be a universal day, and that day would start at mean midnight at the initial meridian. From that moment, the space and time on our globe have been universally coordinated.

Having a single prime meridian brings to the world's cartographers a universal map language allowing them to join their maps together, facilitating international trade and maritime navigation. At the same time, the world now had one matching chronology, a reference by which today you can tell what time of day it is anywhere in the world simply by knowing its longitude.

For decades, the Moon’s subtle gravitational pull has posed a vexing challenge — atomic clocks on its surface would tick faster than those on Earth by about 56 microseconds per day. This extremely small difference doesn’t seem like much, but it could disrupt the precise timing needed for important activities like spacecraft landings and communicating with Earth.

Now, researchers at the National Institute of Standards and Technology (NIST) have developed a plan for precise timekeeping on the Moon, paving the way for a GPS-like navigation system for lunar exploration. The research, published in The Astronomical Journal, focuses on defining a theoretical framework and mathematical models necessary for creating a lunar coordinate time system.

This innovation is crucial for NASA’s ambitious Artemis program, which aims to establish a sustained human presence on the Moon and may be an important steppingstone for exploration of the cosmos.

The picture shows my home-built digital clock, using Nixie tubes for readout. In contrast to most other nixie clocks being built these days, this clock does not use any transistor or IC for controlling and driving the tubes. Instead, the driving logic is built from trigger tubes, together with resistors, capacitors and silicon diodes. A video is on youtube.

This project is a followup to a similar clock I built between 2002 and 2007, documented on its own page. That clock used regular NE-2 style neon lamps as logic elements. Unfortunately, after a while, as these lamps aged, the clock became unreliable and unusable.

The new clock uses trigger tubes, of the МТХ-90 type (that's in Cyrillic characters; transliterated to Latin script it's MTH-90), which are widely available as "new old stock" on Ebay. Trigger tubes are essentially regular neon lamps with an extra "trigger" electrode, which can be used to ignite them. However, in this circuit I don't use the trigger electrode.

The above shows my home-built digital clock. It uses Nixie-tubes for readout. In contrast to most other nixie-clocks being built these days, my clock does not use any transistor or IC for driving the tubes. Instead, the driving logic is built from neon lamps, together with resistors, capacitors and silicon diodes.

The project started in 2002, when our university library was selling old outdated or otherwise superfluous books, and I very cheaply bought the book "Electronic Counting Circuits" by J.B. Dance, published in 1967, and apparently only ever lent three times by our library, all in 1973. It described how neon lamps can be used as logic elements in a ring counter, exploiting the fact that they need a higher voltage to ignite (the striking voltage) than to stay lit (the maintaining voltage):

The Hafele–Keating experiment was a test of the theory of relativity. In 1971,[1] Joseph C. Hafele, a physicist, and Richard E. Keating, an astronomer, took four caesium-beam atomic clocks aboard commercial airliners. They flew twice around the world, first eastward, then westward, and compared the clocks in motion to stationary clocks at the United States Naval Observatory. When reunited, the three sets of clocks were found to disagree with one another, and their differences were consistent with the predictions of special and general relativity. //

Hafele, an assistant professor of physics at Washington University in St. Louis, was preparing notes for a physics lecture when he did a back-of-the-envelope calculation showing that an atomic clock aboard a commercial airliner should have sufficient precision to detect the predicted relativistic effects.[11] He spent a year in fruitless attempts to get funding for such an experiment, until he was approached after a talk on the topic by Keating, an astronomer at the United States Naval Observatory who worked with atomic clocks.[11]

Hafele and Keating obtained $8000 in funding from the Office of Naval Research[12] for one of the most inexpensive tests ever conducted of general relativity. Of this amount, $7600 was spent on the eight round-the-world plane tickets,[13] including two seats on each flight for "Mr. Clock." They flew eastward around the world, ran the clocks side by side for a week, and then flew westward. The crew of each flight helped by supplying the navigational data needed for the comparison with theory. In addition to the scientific papers published in Science,[5][6] there were several accounts published in the popular press and other publications. //

Presently both gravitational and velocity effects are routinely incorporated, for example, into the calculations used for the Global Positioning System.

Our beloved NTP protocol appears to work in a deep space environment (as tested in a simulation with a 4 hour RTT):

https://deepspaceip.github.io/testbed/ntp.pdf

PTP daemon (PTPd) is an implementation the Precision Time Protocol (PTP) version 2 as defined by 'IEEE Std 1588-2008'. PTP provides precise time coordination of Ethernet LAN connected computers. It was designed primarily for instrumentation and control systems.

No, you do not need to set all Livewire devices to be a PTP clock slave. Some devices that aren't fully AES67 compliant can only accept Livewire clock.

What's important is any clocks are all synced together, somehow, so they both have the same reference.

Can we use research and policy to change (or not change) the clocks for the last time? //

In 2022, Gentry and an interdisciplinary team of colleagues added to that body of research, publishing a study in the journal Time & Society that showed the rate of fatal motor-vehicle accidents was highest for people living in the far west of a time zone, where the sun rises and sets at least an hour later than on the eastern side. Chronobiology research shows that longer evening light can keep people up later and that, as Gentry found, morning darkness can make it harder to get going for work or school. Western-edge folks may suffer more deadly car wrecks, the team theorized, because they are commuting in the dark while sleep deprived and not fully alert.

With all the hullabaloo over the health and safety of setting clocks forward an hour in the spring for Daylight Saving Time (DST) and back in the fall with Standard Time (ST), could where you live in a time zone actually have a more profound effect? I asked Gentry. “That’s very possible,” he said.

Time researchers make this point, and research results and public opinion polls reflect it: Something is awry about the way we mark time. //

Permanent DST meant that the sun also rose and set later in the winter. Results published in 2017 associated year-round DST with a greater likelihood of feeling down in the winter as well as sleeping later on weekends, a phenomenon known as social jet lag. Chronobiologist Till Roenneberg and colleagues coined the term nearly two decades ago to describe the chronic sleep deprivation that people experience when they have to get up for school or work before they would awaken naturally. //

“We all agree as researchers that the safer option is to go for perennial Standard Time,” said Blume, a postdoctoral researcher at the University of Basel in Switzerland.

The nonprofit organization Save Standard Time lists endorsements from more than 30 sleep-science and medical organizations—including the American Academy of Sleep Medicine, the American Medical Association, and the American Academy of Neurology among others—in addition to individual scientists and researchers.

Here, I feel compelled to note that the last time we tried permanent DST, it didn’t go well. In attempt to conserve energy, Congress established a trial period of year-round DST in late 1973. But public approval dropped precipitously as Americans faced the reality of dark winter mornings. By October 1974, the country had reverted to four months of yearly ST. //

Things gets interesting on either side of a time-zone boundary, where the sun position is essentially the same, but the clock time is different. In late January, for example, the sun sets around 6:10 pm in Columbus, Georgia in Eastern Time, but at 5:10 pm just over the time-zone border in Auburn, Alabama.

People living on the late-sunset side of a time-zone border, like those in Columbus, tend to go to bed later, sleeping an average of around 20 minutes less each night than those on the early-sunset side, like those in Auburn, according to a 2019 study published in the Journal of Health Economics. Drawing on large national surveys and data from the Centers for Disease Control and Prevention, researchers found that health outcomes associated with sleep deficiency and social jet lag were worse for the late-sunset folks. Their wages were also about 3 percent lower than those of early-sunset people, who, better rested, were presumably more productive. //

Another tricky aspect of time zones is that they don’t strictly adhere to longitude lines but instead meander to accommodate city and state boundaries. In the US, all the time zones except Pacific Time encompass areas west of what would be the natural time-zone boundary. Communication professor Jeffery Gentry and a team that included Eastern New Mexico University professors with expertise in geography, biology, and education have dubbed those regions west of the geographic time zone “eccentric time localities,” or ETLs.

In these ETLs, sunrise and sunset time may occur more than an hour later than the eastern side of the time zone. For example, geographically, Marquette, Michigan, should be in Central Time, but instead, the city lies in an ETL in Eastern Time. In late October, the sun rises at around 7:10 a.m. Eastern Time in Bangor, Maine, but not until around 8:30 am in Marquette. //

Gentry would like to see time zones redrawn. But other policy fixes could help as well. //

A body of research shows that even dim light can suppress melatonin production and delay sleep. Blue light from fluorescent lights and our ubiquitous screens, which has the shortest wavelength and highest energy of light that the human eye can see, has a particularly powerful effect on circadian rhythms. //

And, although it sounds like a radical idea, states could also adjust time-zone boundaries. “I don’t think we want 10 time zones, but maybe we add one for the Northeast,” said Malow. Because the New England states are so far east, winter sunsets come early—before 4 pm in December in parts of Maine. //

nimelennar Ars Praefectus
6y
8,590
Subscriptor
Dzov said:
lol. Make sunup and sundown always 8am and 8pm respectively and your work day lengthens and shortens throughout the year and based on your latitude.
You can work at the North or South Pole. You punch in at 8 a.m., and punch out at 8 p.m., six months later.