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Your questions on the upcoming leap second

Just back in the office from a trip, I found several questions in my email box in regard to the upcoming leap second. I thought that I’d take a moment or three to answer several of the questions there, some not covered in past posts.

The first question on everyone’s mind could be summarized best as…

“Is there anything special I need to do to my computer or tablet?” (related questions included: Is there a hotfix for this leap second? When will I see the update applied? Will most average computer users notice the leap second? Is there anything they should do to prepare?)

Generally, as a Windows computer user, there’s nothing in particular to do – no special updates or hotfixes to apply. As I covered in this earlier post (and also summarized here), current supported versions of the Windows OS are plumbed to deal with such additional leap second. It’s recommended that you set your PC to sync with an Internet time server via the Control Panel in Windows 7 (as noted here), or in the PC Settings for “Time and Language” on Windows 8.1 (as shown here). With that done, you should be good to go. (If you’re device is part of a domain – such as PC provided by your company for business – then your clock sync is likely managed by your IT administrator.)

As called out on the Windows site with instructions on How to Set the Clock, you can sync your device clock with an Internet time server of your choice to help ensure your device’s clock is accurate. Typically time is updated once a week when your device is connected to the Internet, or the clock sync may be managed by your administrator (with domain joined devices). As a user, you probably won’t notice the extra second nor see any impact to your Windows devices.

Next was on the impact of the leap second on devices…

“Will this leap second cause any problems on my system?”

Generally, no, as my associate Matt Johnson noted. Usually leap seconds don’t cause a problem unless you are timing things less than a second in duration, or if you are re-sorting events that occur in high frequency. As Matt called out, most software applications and services have to cope with minute time adjustments to the system clock for a variety of other reasons anyway, and leap seconds are no different. I say “generally” as folks who need highly accurate time sources should refer to the detailed post on high accuracy W32time requirements on how to configure the Windows Time service for high accuracy environments and Kerberos standards. (NIST’s Physical Measurement Laboratory provides a list of several high accuracy manufacturers of time and frequency hardware receivers and software providers.)

Next was on the hype around this new leap second contributing to a Y2K event…

“I heard that the last time we had a leap second, the Internet melted down.” (Related: [Some have] compared this to the Y2K problem. Is that an accurate comparison? Will there be a massive disruption of computers and services? )

First, that’s not really a question but a statement I have heard a number of times, and not a true statement at that, as I noted in this appropriately titled post. Some reports (like this one in USA Today) were quick to associate the addition of a leap second in 2012 to the bug that “took down much of the Internet.” Generally, consumers have nothing to worry about when it comes to this non Y2K event: the timing of the 2012 leap second happened to unfortunately coincide with a power outage that impacted their service provider (as noted by the BBC). Yes, there were some reported impacts as noted by Robert McMillan at Wired in his post “The Leap Second Is About to Rattle the Internet. But There’s a Plot to Kill It”. But when the last leap second adjustment was made (back on June 30, 2012), I don’t believe we at Microsoft had any reports of leap second related issues for any of our products including Windows and Azure (or any customer applications running on Azure).

Then there’s a question about services…

“What about online services?”

Similar to connected devices that rely on NTP, various cloud systems also obtain NTP sync in similar ways, keeping in mind that cloud services aren’t just fluffy concentrations of water vapour but (in our case) more than 100 global datacenters supported by a multi-terabit global network. How leap seconds are applied to and appears on a local machine clock may be different from an online service but share many of the same traits as documented and understood in Windows, upon which Microsoft Azure has its origins. In speaking with the Azure team, I learned the service has been designed to be resilient to clock discrepancies across our numerous infrastructure components and regions. Azure has proven application compatibility for handling leap seconds given it uses the Windows time-synchronization protocol, which is used by all Windows systems.

And then this question about when to adjust your watch…

“Should I set my watch at midnight?” (related: Is this similar to New Year’s or the adjustment for daylight saving time?)

Unless your watch is accurate to the second, or you happen to live in an area like Casablanca, Morocco, no. Contrary to some media reports, the change does not happen at midnight local time in each time zone, unless that time zone currently has a zero offset from Coordinated Universal Time or UTC (en Francais, temps universel coordonné) meaning the country uses the UTC+0 offset (like Morocco). For me and my compatriots in Redmond (which is UTC -7:00), the leap second will be added on June 30, 2015 at what essentially will be 4:59:60PM local time. And it doesn’t hit everywhere on June 30: some time zones will see the leap second added on July 1: folks in London will see a leap second added on July 1, 2015 at 12:59:60AM, and Paris (to which my watch is still set) at just before 2:00AM local time.

Further, unless you’re managing a satellite or a space mission, leave the update to your system: there’s no need to ping the time server manually. If everyone in the world called the Internet time servers at the same time, there could be a strain on the server. 

[063015: I saw another example of the above error on NBC’s “Today Show“, whereas their competitor over on ABC got it right.]

I also received questions on the various approaches of how system providers plan to accommodate the a leap second. Aside from how Microsoft syncs the system clock to the accurate time, I’ll leave the explanations of the benefits and potential drawbacks of the approach to those companies.

 

Also available at https://aka.ms/leapsecqna

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Another look at the impact of the coming 2015 leap second on Microsoft products (not much)

Drawing of a man holding back the hands of a clock with the caption "You can't stop time"A month from now, we should be looking back at the press that decried the coming Leap Second (caps my own) as a veritable Y2K and wondering “what was all that about?” As I’ve shared previously (see “What’s all this about the Leap Second”) I’ve learned quite a bit about how Microsoft products and services address the addition of a new leap second. Most often, issues of time and date are addressed by the groups involved in managing the Windows OS, plus in this instance by the team managing the Windows Time service. Many of our products and services rely on the underlying OS for time and date, much like the support for daylight saving time and time zone support. There’s a great TechNet post that covers How the Windows Time Service Works.

What you likely need to know: On the Windows Client, current supported versions of Windows are plumbed to deal with such leap second changes via an NTP ping in the Windows Time service (a.k.a. W32Time), as I summarized here. As you may know, W32Time handles regular clock sync, and as root time sources are updated, changes propagate through NTP and adjust network synched clocks. I outlined much about what you may want to know in my post on the story around Leap Seconds and Windows. Essentially, set your PC to sync with an Internet time server via the Control Panel in Windows 7 (as noted here), or in the PC Settings for “Time and Language” in the Control Panel on Windows 8.1 (as shown here), and you’re good to go. (If you’re device is part of a domain – such as PC provided by your company for business – then your clock sync is likely managed by your IT administrator, so again, you should be good to go.)

Background on how a leap second is added: When a leap second is to be added, a notification is broadcast on the day of the event (sometimes in the hour prior) via an NTP flag from the NTP server to all NTP clients. Time services (e.g., time.windows.com) sync with authoritative, atomic clock time servers such as those maintained by the National Institute of Standards and Technology (a.k.a. NIST, at bldrdoc.gov). These facilitate regular clock sync, and as the root time sources are updated, changes propagate through NTP and adjust network synched clocks as well. Technically, IIRC, the leap second is applied by NIST on NTP as a second iteration (a repeat, actually, in binary) of the final second of the day, and would look something like this: “23:59:58… 23:59:59… 23:59:59… 00:00:00UTC”. (BTW, some systems interpret this last second as 23:59:60.) Think an abbreviated, one second version of the issue Emily Blunt faced in Edge of Tomorrow, but without all the bloodthirsty aliens and general mayhem.

How a leap second is reflected in Windows: Contrary to one post I recently read, Microsoft doesn’t implement a leap second time zone by time zone – in other words, in a rolling fashion, like the way we watch new year celebrations count down around the world. Essentially, the leap second occurs at the same time everywhere. Just when your individual device syncs with NTP will likely be different from others. Windows devices that are joined to a domain will attempt to sync with the domain hierarchy. Consumer devices that are not domain joined, sync time less frequently or have intermittent network connections sync the clock most commonly to the Microsoft NTP server, time.windows.com. As these systems do not sync the clock frequently, we’ve stated that “it is impossible to guarantee time accuracy on computers that have intermittent or no network connections.”

Devices that are synched with time.windows.com will eventually sync to the current, accurate time reflecting the leap second. As time.windows.com syncs with NIST time servers, Windows devices are generally accurate and in sync subsequent to the addition of the leap second. Many devices will sync within the first few seconds of 00:00:00 UTC (which some may refer to as “midnight UTC”) on June 30, 2015 / July 1, 2015 as they ping the service. But of course, not all systems sync at or close to 00:00:00 UTC. Microsoft has outlined that W32Time service is not a full-featured NTP solution that meets time-sensitive application needs (see Microsoft KB 939322, Support boundary to configure the Windows Time service for high-accuracy environments). Companies that require critical timing systems usually implement a specific reference clocks that provide highly accurate hardware clock, which when used with Windows, use their own incredibly accurate clock drivers. Whereas Windows is supported to be accurate within something like 3 seconds, these clocks are accurate to within <1s. (If you want to get all nerdy, my friend, Matt, reminded me of my desire for a Meinberg clock, and a great summer project you can DIY with your kids.)

How the leap second is reflected in services:  Various cloud systems obtain NTP sync in much the same way. How leap seconds are applied to and appears on a local machine clock may be different, but this is well documented and understood in Windows, upon which Azure has its origins. (More on that in a second – see also the info in Microsoft KB 909614, How the Windows Time service treats a leap second, and KB 939322, Configuring the Windows Time service for high-accuracy environments.)

In speaking with the Azure team, I learned the service has been designed to be resilient to clock discrepancies across our numerous infrastructure components and regions. Azure has proven application compatibility for handling leap seconds given it uses the Windows time-synchronization protocol, which is used by all Windows systems including the Windows client OS, Windows Server, Windows Phone, and Hyper-V. When the last leap second adjustment was made (back on June 30, 2012) we had no reports of leap second issues for any of our products across Windows, Azure, or the customer applications running on Azure. Similarly, I understand that other Microsoft services, including as Office 365, Dynamics CRM Online, Intune and Azure RemoteApp services, aren’t affected by a  leap second change. I’ll add additional information here as I come across it.

Generally, Microsoft products (e.g., Exchange, Office) and most/all third party apps rely upon W32Time to provide an authoritative view of time, using UTC rather than local time (the time you see displayed by your Clock app and in the Date & Time display). As long as the OS is able to manage the leap second change, dependent applications should generally be fine: there could be implications for apps or services that do not follow standard clock implementations. If an app or service uses another time sync method or has other time dependencies then there could be an impact (e.g., presenting an app with a time reference of 23:59:60 when it doesn’t expect to see seconds greater than :59). More info on some of these concepts with appropriate links here.

Article also available at http://bit.ly/leapsecinfo

[edit: added information in ¶2 on domain-joined devices; added detail in ¶3 on the binary nature of the leap second via NIST]

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The story around Leap Seconds and Windows: It’s likely not Y2K

Today I woke to a number of hair-on-fire press articles decrying the coming and dreaded Leap Second… with the mainstream USA Today calling out…

“But last time it happened, in 2012, it took down much of the Internet. Reddit, Foursquare, Yelp and LinkedIn all reported problems, and so did the Linux operating system and programs using Java.”

Not quite correct: IIRC, although some may’ve succumbed to bugs noted in Wired, several popular Internet services (including some of those mentioned) went off line due to a serendipitous and unfortunately timed power outage that impacted their service provider as chronicled by the BBC.

So, why isn’t Windows mentioned?

Glad you asked.

As I noted a couple of years ago, you’ll find more documenting the impact of a leap second in heartwarming Knowledge Base article “How the Windows Time service treats a leap second” and (excerpted) for everyman by the well-read and  Michael Kaplan. Essentially, after the leap second occurs, the NTP client that is running Windows Time service is one second faster than the actual time. This time difference is resolved at the next time synchronization.

“In short, W32Time does not account for a leap second being dependent on the NTP server. Most applications and services may be unaffected, but sysadmins and IT professionals should know that the leap second is not addressed until the next time sync following the official addition/ subtraction of the leap second.

“KB 816042, How to configure an authoritative time server in Windows Server 2003, and KB 884776, How to configure the Windows Time service against a large time offset.

As The Telegraph noted, “Many computing systems use the Network Time Protocol, or NTP, to keep themselves in sync with the world’s atomic clocks.” As called out on the Windows site with instructions on How to Set the Clock, you can sync your device clock with an Internet time server of your choice to help ensure your device’s clock is accurate. Typically time is updated once a week (when connected to the Internet – who isn’t?), or the clock sync may be managed by your administrator (with domain joined devices). As a user, you probably won’t notice the extra second nor see any impact to your Windows devices.

In addition to the historical blog record in the Windows Time Service blog, more articles/ information in which you may be interested:

Generally, consumers have nothing to worry about when it comes to this non Y2K event. IIRC, the concept of a leap second is actually in question, and an ITU working group has debated whether or not adding/subtracting leap seconds should be discontinued (as noted here). We’ll see what 2015 brings. Or January, 2038 for that matter.

BTW, a few additional notes today from my associate and venerable time lord Matt Johnson…

“It may be worth noting a couple of things from a developer’s perspective:

  • Most applications do not handle leap seconds, as their time structures only allow seconds numbered to 59 – not to 60.
  • Most applications do not care about this, as they will never receive a leap second from the system clock – even when one occurs.
  • Most applications have to cope with minute time adjustments to the system clock for a variety of other reasons anyway – so leap seconds are no different.  Consider that clock drift does occur, and is often corrected by NTP sync – so it’s not abnormal for an app to receive timestamps out of sequence.
  • Depending on implementation, sometimes a system just won’t observe the leap second at all, but that just means its clock will be off by one second until the next NTP sync.
  • Even when the leap second is observed perfectly, it only affects code that needs to be precise to sub-second accuracy.  Consider how the clock will tick over an observed leap second when you observer it by tenths of a second: 23:59:59.8, 23:59:59.9, 00:00:00.0, 00:00:00.1

“So, it usually doesn’t cause a problem unless you are timing things less than a second in duration, or if you are re-sorting events that occur in high frequency.”

[Note: Part two of the story around Leap Seconds and Windows: #NotY2K]

Also available at https://t.co/8ZVoch44QO

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It’s Time To Fall Back An Hour in the US and Canada: Daylight Saving Time Ends This Sunday

Drawing of a man holding back the hands of a clock with the caption "You can't stop time"

How quickly time flies, seems like just yesterday we were Springing Forward (way back on Sunday, March 11). Yes, it’s that time again if you’ll pardon the pun, to fall back in much of the Northern Hemisphere.

Daylight Saving Time ends on Sunday, November 4, 2012 at 2:00AM local time in much of the U.S and Canada, except in parts of the countries (including Hawaii and Arizona). For some folks in my old home north of the boarder, Daylight Saving Time means most Canadians will get an extra hour of sleep. Our friends in much of Europe have already bid goodbye, adieu, auf wiedersehen, gesundheit, farewell to European Summer Time, as they fall back on the last Sunday in October each year. (Not to worry, they’ll get back up and Spring forward again on the last Sunday in March.) For our friends in Russia, I’m not sure what the next few months will bring given the back and forth we’ve seen in the country in regard to policies, but safe to assume for now there is a state of détente in the Federation.

You can read more than you’ll ever want to know about DST here and on our official Microsoft Daylight Saving Time Help and Support Center at http://www.microsoft.com/time. DST in much of the US and Canada ends in accordance with the US Department of Energy’s Energy Policy Act of 2005 that was passed into law. DST ends later than it did prior to 2007, on the first Sunday of November; more details on the new DST start and end times can be found here). This results in a new DST period that is approximately three to four weeks longer than in past years.

Also important to note, but often ignored: the switch to daylight saving time also means the time zone suffix changes in North America, now using Daylight Time: for example, Pacific Standard Time is now Pacific Daylight Time (aka PDT). The other time zones move to Mountain Daylight Time (MDT), Central Daylight Time (CDT), and Eastern Daylight Time (EDT).

National Geographic has a very interesting article on “Daylight Saving Time – Why and When Does It End” (including a very cool photo of the display model of the inner workings of a clock at the China Science and Technology Museum in Beijing). As you may know (especially if you’re geek familiar with my woefully ignored blog – been busy!) the quite historical Benjamin Franklin pioneered the daylight saving time, as noted in David Prerau’s book Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time. And of course, you’re likely much too young to recall the move by the U.S. Government in the 1970s to extend DST (back when the price of gas jumped nearly 50% to about 55 cents a gallon in the States)…

“During the 1973-74 Arab oil embargo, the U.S. once again extended daylight saving time through the winter, resulting in a one percent decrease in the country’s electrical load, according to federal studies cited by Prerau.”

“OK, that’s all nice and such, but what do I need to do besides set my kitchen clock back an hour?”

As I noted in this article, Microsoft strongly recommends that DST and time zone updates be installed on all affected systems, devices and applications to ensure consistency with current DST rules and time zone settings worldwide. Customers should review the product updates available and posted on this site and at http://support.microsoft.com/gp/dst_prodlist for the latest and updated information of Microsoft products affected by daylight saving time.

Here’s more coverage on DST this year from Bing News.

On a personal note, remember to keep things in perspective. Time is a precious thing. Never waste it…

Have a good weekend, and don’t keep too much of that Halloween candy around. As noted here, you can thank candy makers for some of the politics behind DST.

Tags: Microsoft, Daylight Saving Time, Daylight Savings Time, DST.

References to DST on Bing: 1,700,000.

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Also available via http://bit.ly/SyW30e

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Update: No immediate plans in Russia to return to Winter Time in 2012

A few days ago I mentioned the discussion that Russia may return to Winter Time in 2012.

I now have news that legislative initiative of the State Duma Health Committee to switch Russia back to the “winter time” has been withdrawn. As such, we don’t believe there will be any near-term change to Russia’s time zone offset for what we refer to commonly as Daylight Saving Time, or any immediate move in the Federation to move their clocks again. We believe the issue will be considered by the Government and will continue to watch the issue.

Tags: Microsoft, Daylight Saving Time, Daylight Savings Time, RSS,DST, Russia

Also available via http://bit.ly/V1jEcw

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