The future of Coordinated Universal Time (UTC): Experience and views in Australia APT Information Session on WRC-15 Agenda Item 1.14 Bangkok, 10 February 2015 Dr Bruce Warrington General Manager, Physical Metrology National Measurement Institute

Outline: Some experience of leap seconds in Australia, and current views Based on surveys conducted to date, some follow-up conversations, and experience at the National Measurement Institute, which:  Maintains, develops and disseminates Australia’s standards of measurement  Works closely with international standards institutes and other government agencies  Provides a range of timing services to industry and the community

Proposed methods Introduce a continuous reference time-scale and stop insertion of leap second Method A1: stop the insertion of leap seconds in UTC to be effective no less than five years after the date of entry into force of the Final Acts of the WRC-15; Method A2: similar to A1 but also change the name of UTC. METHOD A: Retain UTC as currently defined and introduce a continuous reference atomic time-scale based on TAI with an offset to be broadcast on an equal basis. METHOD B: No change to UTC: Method C1: No change UTC definition in Rec. ITU-R TF.460-6, UTC will remain the only time-scale that is broadcast; Method C2: similar to C1 but also Rec. ITU-R TF would be amended to allow using continuous system time-scales in addition. METHOD C:  Need to evaluate benefit, effort and risk  These apply to all of the proposed methods: even the status quo requires work to implement and has both advantages and risks  Overall, Australia is in favour of Method A (option A1 or A2).

Midnight UTC10 am Sydney  Leap seconds occur during the morning in the Asia-Pacific  Any impact affects the start of the business day Leap seconds and time zones

 Leap seconds do not occur frequently, so there can be significant change to systems and staff in between  This will be the first leap second for almost twenty years that takes place on a ‘normal’ business day (leap seconds on December 31 UTC fall on January 1 in Australia, a public holiday; 30 June 2012 was a Saturday and 1 July 2012 a Sunday) A history of leap seconds

Our infrastructure is held together by time—from time stamps on complex financial transactions to the protocols that hold the internet together. When the packets of data passing between computers get out of sync, the system starts to break down. Without accurate time, every network controlled by computers is at risk. Which means almost everything. Richard Hollingham Networked time  Network Time Protocol is designed to handle leap seconds, but in practice no leap second has been handled perfectly.  In 2012, about 10% of the ‘NTP pool’ got it wrong. Most NTP servers were fixed within an hour, but some took up to a day. Some added the leap second on the wrong day. D. Matsakis, USNO

2 July 2012

 Qantas worldwide booking system (Amadeus) disrupted for more than two hours  Staff forced to switch to manual check-in process  More than 400 flights delayed What happened in 2012?  Qantas and Amadeus made reasonable and prudent operational decisions to prepare for the leap second  Amadeus subsequently reported that the issue was caused by a bug in the Linux operating system  Online reports from system administrators and programmers showed that the bug had been present in the kernel for a long time, and not found through testing

ASIC Market Integrity Rules (Competition in Exchange Markets) 2011 Potential impact on financial markets

 Market rules require market operators to synchronise clocks to UTC  Leap second occurs at 23:59:59 UTC Tuesday June 30  Local time in Sydney in June is UTC+10  Leap second occurs at 9:59:59 AEST Wednesday July 1 (Australian Eastern Standard Time)  Equities markets open for trading at 10:00:00 AEST  All market operators, and all market participants, must correctly apply the leap second to begin trading at the same time and at the right time  (Note: AEST is defined by offset from UTC, so this would still be true even without the market rule on synchronising to UTC) Potential impact on financial markets

 Users need to know that they must allow for leap second: Timekeepers know, but users in other fields may not  Users must allocate resources to prepare: Software development, test platforms, scenario testing Computer systems change rapidly (new functions or hardware); even in older systems, new components must be tested Users may not have expertise to understand all the tests required  In practice it may be impossible to guarantee correct performance: Recent leap seconds have all caused some problems, despite significant preparation and learning from past mistakes Critical dependence on other systems (GPS receivers, NTP servers, operating systems, application software…) Effort and risk of UTC with leap seconds

CSIRO ATNF Parkes, NSWASKAP Murchison, WACDSCC Tidbinbilla, ACT AAO Siding Spring, QLDANU Mount Stromlo, ACT Astronomy in Australia

Precise time in astronomy  Needed for antenna pointing and tracking: Offset between UTC and UT1 is known very accurately and in advance This offset is always below one second; stopping leap seconds would require software changes  Also needed for long data series: Astronomers must know the history of changes to the time scale when comparing observations over long times (eg pulsars) VLBI data also used in geodesy and national mapping  Overall, astronomers are broadly in favour of ceasing leap seconds, though some are opposed

10 µs 20 years R. N. Manchester Australia Telescope National Facility Pulsar timing observations  Pulse periods affected by the presence of gravitational waves  Observations can test fundamental theories and may allow direct detection of gravitational waves PSR B Parkes Pulsar Timing Array

Offset between UTC and solar time  The day was ~30 ms shorter in 136 BC, and the Earth has ‘lost’ 3 ¼ hours since then  If leap seconds are stopped, the offset between UTC and UT1 will be around 1–2 minutes in 2100

Offset between UTC and solar time  Some argue that ‘breaking the link’ between clock time and solar time is a fundamental change: My view is that without leap seconds we will eventually lose the link between time and people's everyday experience of day and night (David Willets, UK)  Others argue that we cope with much larger differences between these two time scales already: We adopt ‘time zones’ which standardise clock time up to an hour (or more) different to solar time We change by an hour twice a year for daylight saving Solar time varies by around 15 minutes over a year (the ‘equation of time’) By comparison, 1–2 minutes may not be significant. Sandford Fleming

Civil time in Australia: time zones Local time is UTC plus: (  daylight saving)

South Australian Government time zone shift will be good for business, Premier says Fri 6 Feb 2015 A State Government proposal to change South Australia's time zone is aimed at making the South Australia more business friendly, the Premier says. The Government proposed changing its time zone to align with either the eastern states or Western Australia. SA Premier Jay Weatherill said the half-hour time difference between the eastern states, and the 90- minute difference with Western Australia, could cause "confusion across the spectrum of our daily lives". "The business community has raised this issue with me on a number of occasions and I believe the time is right to put the broader question to the community about the day-to-day inconvenience of a half-hour time zone," he said.

Proposed methods Introduce a continuous reference time-scale and stop insertion of leap second Method A1: stop the insertion of leap seconds in UTC to be effective no less than five years after the date of entry into force of the Final Acts of the WRC-15; Method A2: similar to A1 but also change the name of UTC. METHOD A: Retain UTC as currently defined and introduce a continuous reference atomic time-scale based on TAI with an offset to be broadcast on an equal basis. METHOD B: No change to UTC: Method C1: No change UTC definition in Rec. ITU-R TF.460-6, UTC will remain the only time-scale that is broadcast; Method C2: similar to C1 but also Rec. ITU-R TF would be amended to allow using continuous system time-scales in addition. METHOD C:  Need to evaluate benefit, effort and risk  These apply to all of the proposed methods: even the status quo requires work to implement and has both advantages and risks  Overall, Australia is in favour of Method A (option A1 or A2).

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