Daylight Saving Starts
On Sunday 2017-03-12 at
2AM, you need to move your wall clocks, alarm
clocks, watches, timers and appliance clocks forward one hour to 3AM. In the strange world of DST (Daylight Saving Time), there is no
time between 2AM and 3AM. You can also do it before you go to bed, or after
you wake up tomorrow.
- Your computer should change your clock automatically. If it
fails to show the correct time, use the SetClock
to correct it from an atomic clock on the web. If you do it
manually, chances are you will leap too many hours.
- If you have Windows, read the Windows
Time Entry to learn how to configure your clock to stay in
for the life of your computer.
- If you own a radio-synced
wall clock or watch it should automatically correct itself.
By putting forward the hands of the
clock you shall not advance the hour.
~ Victor Hugo
(1802-02-26 1885-05-22 age:83)
summer time or war time.
The British call it
BST (British Summer Time),
The French call it heure
d'été. The Germans call it Sommerzeit.
The Dutch call it Zomertijd.
It is a scheme to get people to wake up earlier and go to bed earlier
to save electricity. You set clocks ahead a hour (or more) in spring
and set them back in the fall. Commonly, you set the clock an hour
forward at 2:00 A.M. on the second Sunday in March)
and set it back one hour at 2:00 A.M. on the first Sunday in
November. You can remember with the mnemonic spring
forward, fall back.
In North America, in the spring you set the wall clocks ahead and in the
fall you set them back. Think “Spring forward, fall back“.
In the fall at 2AM on a designated Sunday, you roll the clock back to
1AM, giving you a duplicate hour between 1 and 2AM to sleep. Think about
bears hibernating in the fall and getting extra sleep. In the spring at
2AM on a designated Sunday, you roll the wall clocks forward to 3AM,
skipping out the entire hour between 2 and 3 AM. So you get an
hour’s less sleep. You get up an hour earlier, measured by the
sun. Think of yourself springing eagerly from bed an hour earlier than
Around the World
globally is not as simple as in North America. The rules vary over
time and by jurisdiction.
In British Columbia, Canada, where I live, local time is
UTC (Coordinated Universal Time/Temps Universel Coordonné)
minus 8 hours for
PST (Pacific Standard Time)
minus 7 hours for
PDT (Pacific Daylight Time).
starts on the second Sunday in March and ends the second Sunday in
Newfoundland is odd in that it in not an even hour difference from
GMT/UTC. Newfoundland Standard Time is
minus 3.5 hours. It also odd in that they do the
flip at 00:01 AM rather that 02:00
AM like the rest of Canada.
all kinds of headaches for computer programmers:
- In the spring, there is a missing hour. If you are not careful
your payroll program will pay people for an hour they did not work.
- In the fall, the are two different times, both 1:30
AM. The first is 1:30 AM
daylight time and the second, a hour later, 1:30
AM standard time. Any time keeping must maintain the
distinction. The distinction only matters during one hour each year.
- The dates that daylight saving starts and end change year by year
and city by city. Your only hope is to convert all times to
GMT (Greenwich Mean Time),
then do your elapsed time calculations and use locale tables to
convert them back for display to local time. The Java Timezone
class contains the locale-specific information to do these
- Badgers in Britain normally do not come out of their burrows until
traffic is light. The
transition in March fools them and twice as many as usual get hit by
- Microsoft did not correct W95, W98, Me, NT and W2K
to account for the extended daylight saving introduced in 2007
in the USA. You can manually fix the problem by downloading TZEdit.exe then
use it to configure the start and end dates on the relevant time
zones to start three weeks earlier (2:00 A.M. on the second
Sunday in March) and end one week later (2:00 A.M. on the
first Sunday in November). Canada follows the USA.
- Sundials do not understand DST.
- Some devices need the flip. Some do not. It is easy to flip a
device that does not need it and fail to flip one that does not. In
the old days there was one wall clock and one watch per household.
Today there are dozens of clocks. It is easy to forget
one. One year I missed flipping an alarm clock and I missed an
appointment that could not be rescheduled for 6 months.
Arguments for dropping
- The Rachael Maddow show trashed
- If we abolished
people would still likely want to get up earlier in the summer.
Businesses would then stagger their hours shifting throughout the
year, perhaps in smaller increments than an hour. Because everyone
would not make these shifts in sync, it would flatten out peak hours
in traffic and electricity usage thus providing billions in saving
not to mention less-congested traffic.
- Despite the assurances of the Bush administration,
does not save energy. With the extra evening daylight hours, people
drive to the mall or ballpark. It is a retail stimulus and a way to
increase gas consumption.
- The original story was we did it for the farmers. However, they
strenuously opposed it when it was introduced. It gave them one less
hour after daybreak before the city markets opened.
- I wonder how many people have been killed by the anomalies when
the time changes. I could imagine some incompetent maker of medical
pumps giving a double dose, or skipping a dose.
- The complication of the
shifts must be handled by every computer program that handles time 24/7. Programmers often do it correctly. The
shifts complicate the code, increases the likelihood of bugs,
increases costs and increases the likelihood of data errors.
- Since, in general, clocks do not automatically adjust for
the manual adjustments trickle in over the next few days, with some
clocks not corrected at all. This creates a limbo period where time
cannot be accurately determined, since one never knows for sure if a
clock has been corrected already, or has had a double correction.
Even official time sources can be off. Shaw TV for example set their
clock ahead around midnight instead of 2:00 AM.
clocks are now relatively inexpensive. Perhaps they will
eventually replace conventional clocks and
shifts can be automatic and bang on punctual.
- Anyone who has to coordinate actions of many people should be
tracking time in
- It is a full-time job just to track the changes in
rules in various parts of the world. The information must be include
in every international computer program. It is perpetually
- Putin commanded Russians to stop fiddling with their clocks. Oddly
he did this in the summer. Russians are now stuck year round in
- Fiddling with the body clock causes heart attacks, traffic
accidents and muddled thinking.
- I once changed all my clocks, but forgot a rarely used alarm clock. The result I was one hour late for a medical appointment.
- Cows and pets will not adjust their schedules just because you fiddled your clock.
Arguments for Keeping
- Abolishing it would require difficult-to-obtain political
- Debate would take away from much more important issues.
- It would require changing computer programs to make them simpler.
shifts are a good time to resync manual clocks.
shifts are a good time to replace batteries in smoke alarms.
provides one more reason to store all dates in
format in databases.
- With DST you spend more of your time driving in daylight which means fewer accidents. Granted there are more accidents in the spring during the transition due to sleep
- Insist that entire countries or provinces/states have uniform time and DST rules, no tiny variant pockets.
- Get rid of DST and stay on standard time all year round.
- Stay on DST all year round.
- Cycle through 1-hour, 2-hour, and 3-hour DST over the year according to math to maximise daylight. The rules depend on latitude.
- Simplify the timezones to three: one for north and south America, one for Europe and Africa and one for Asia. People living near the edges of timezones may informally
slide business hours earlier or later, ideally not in sync to help smooth traffic flow.
- Use one universal timezone, UTC aka GST (Goods and Services Tax). This would allow people communicating over the globe to be clear, e.g. that report needs to be ready by 20:00 UTC.
This would be the simplest and least error-prone for computer programmers. The problem is you would have to calculate other people’s best default contact times.
Your address book would track best contact times in UTC.
On daylight saving switch days, don’t
set your computer clock forward an hour! Instead, make sure your
machine is configured to the correct time zone and reset your clock
from an atomic time source. It will automatically jump at 2
. If you fiddle the clock, you will screw up the file
timestamps which are kept in time zone-independent,
To make sure your time zone is configured correctly and to set your
clock from an atomic timesource, use the SetClock
utility. Please see the Windows
entry on how to configure your Windows clock and have it
keep accurate time.
Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64
is supposed to automatically keep your clock in sync with a
Microsoft time server, but for me it does not work. I suspect the
problem is it is overloaded. I got it to work by configuring a
non-Microsoft pool timeserver.
Linux automatically probes time servers with
NTP (Network Time Protocol)
to keeps its clock in sync.
The Meinberg people provide free NTP software. It keeps computer clock much more accurate than the builtin Microsoft simple NTP software does. It also automatically adjusts for DST.
I bought a Casio watch that monitors a time signal from Fort Collins to keep perfect time automatically, including automatically adjusting for DST.
It is similar to this one:
Casio Men’s model MTGM900DA G-Shock Stainless Steel Tough Solar Atomic Digital Watch
Someday, computers will have built-in
GPS (Global Positioning System)
units and they will be able to configure the local time zone
automatically. But for now, you must do that manually in the control
- On your first reboot after a daylight saving
change, Vista may set your clock ahead two hours instead of one.
You can fix the problem with SetClock
which will also let you verify your time zone.
- In modern operating systems including
NT, W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64,
if you manually change the time after a daylight saving change,
instead of configuring the time zone and letting it happen
automatically, you might confuse the
OS (Operating System),
with the result that file dates on all your files change by one
- If you let Vista or Linux change the time by itself, your file
dates should not appear to change at a
boundary. This is because the timestamps are kept internally in
and files that were last updated in winter are always displayed in
winter time (even in summer) and files last updated in summer are
always displayed in summer time, even in winter.
timestamps are not kept is
but in local time. This means that
changes will trigger WinZip archived files to be updated, since
their local timestamps change, even when the absolute
timestamp does not.
- The rules for
start and end change over time and different for different
jurisdictions. The tables sometimes also have errors that are
gradually corrected. Keep your Java
JDKs (Java Development Kits)
JREs (Java Runtime Environments)
up to date by periodically downloading and applying the
Prior to standard time, every town kept its own local time. You could
imagine the difficulty that caused once the telegraph and trains were
shrinking the world. So Sir Sandford Fleming invented standard time
zones. The boundaries have jogs to suit the political realities but it
basically brought as much order to the chaos as you could reasonably
However, other people hated the order and deliberately screwed it
up by inventing
with every jurisdiction deciding for itself on just how much
to have. We are working our way back slowly but surely to the old
system, that does not even have the uniformity of solar synching.
The Internet is shrinking the world further. To get ahead of the
curve, perhaps we should set our watches to
or at least the alternate time function, such as I have on my radio-synced desk clock.
You’d think, at least in airports, clocks would also display
as would flight schedules. Once people got used to this, they would
not be confused by changing time zones as they moved west or east
between zones. The lengths of flights would be clearer. Tracking
tummy time would be easier.
It would be a Good Thing™ at least if there were a U.N.
department of time that maintained the official list of time zones
rules. It is a difficult job. It should not be duplicated.
To get an idea what a nightmare
has created have a look at Oracle’s
changes. The list is so huge, it can never be accurate.
To make sense of time every computer program needs a giant database
that not only tracks what every micro jurisdiction is doing to
meddle with time, but all they have ever done. This is ridiculous.
In most of Canada,
begins and ends at 2 AM on the same days
as the USA. However, in Newfoundland and Labrador,
begins one minute after midnight local time on the second Sunday in
March. On the first Sunday in November time returns to standard at
one minute after midnight local time.
A few areas of Canada don’t use
at all including Fort St. John, Charlie Lake, Taylor, Dawson Creek
and Creston in British Columbia and most of Saskatchewan (except
Denare Beach and Creighton).
daylight savings change dates in the USA and
|Daylight Savings Change Dates in the USA and
Other countries use different dates or don’t use
at all. They may use the same time zone, but have different
rules. That’s why you don’t configure your time zone
directly in the
but rather chose a city with representative
The TimeZone Database
Arthur David Olson dedicated his life to maintaining a database about
Individual cities change their minds annually about the begin and
end date/times for
The boundaries of the world’s timezones are constantly being
tweaked. Every international computer program in the world has to
incorporate all this historical lore to function properly. Paul
Eggert is the new editor and maintainer of the tz database. Oracle
updates Java with the new information with each release of the
JDK (Java Development Kit)/JRE (Java Runtime Environment).
If you use an old
you will get out-of-date timezone/DST
information. He had some legal trouble with an astrology company
that claimed ownership of such data. Happily, Olson prevailed in the
legal challenge. New versions of Java incorporate the latest
timezone trivia information. Oracle also releases timezone updates
for older versions.