laika
Well-known member
It's not usually done anywhere, although people seem to have started doing it somewhere in the course of this thread.
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Standard Time; is it just me that had it wrong?
- Thread starter richardbrennan
- Start date
It's not usually done anywhere, although people seem to have started doing it somewhere in the course of this thread.
GHA
Well-known member
We do for local and greenwich and local hour angles, which is why it makes perfect sense for anyone having spent time thinking along those lines, it's not about the time on the clock.
It makes perfect sense, just your thought processes use different conventions which make using a different sign make more sense and you can't let go of that, there is no right/wrong.
Buck Turgidson
Well-known member
I suppose in days gone by where a universal time constant wasn't readily available there may have been merit in learning how to find a standard time by correcting the local church clock.
Those days are long gone.
Part of the confusion comes from the idiotic use of terms like "zone time", which is very similar to "Time zone" but means something completely different. Why not use "Local" to indicate "zone time". Then "Local -1" not only indicates the correct adjustment but also the standard to which the adjustment is to be applied.
Those days are long gone.
Part of the confusion comes from the idiotic use of terms like "zone time", which is very similar to "Time zone" but means something completely different. Why not use "Local" to indicate "zone time". Then "Local -1" not only indicates the correct adjustment but also the standard to which the adjustment is to be applied.
Uricanejack
Well-known member
In your opinion...
Makes perfect sense to me, timezone is ahead, to the east, UTC is behind, to the west. Not the time displayed on the clocks in that timezone. Which is another thing altogether.
Think of timezones being 15 degrees of greenwich or local hour angles, east the degrees are less, west is more.
In nav terms it makes sense, imho, timezones and hour angles (greenwich or local) are closely related, west is higher, east is lower, it seems you think more in terms of what is being displayed on the clocks rather than in more celestial nav conventions.
ISTM anyone having played around with celestial nav will find it obvious to have east as a negative and west as positive, everyone else probably the opposite.
Having played with celestial quite a bit. and terestial.
east longitude is posative.
west longitude is posative.
east time posative if you want to figure something out
west time negative.
Naming of time zones, is different. it seams to be going about it ass backwards. starting with local time zone instead of utc.
Its not the first time ive heard this, I have had the argument with a nav instructor as well.
This time I looked it up.
In the 2016 nautical alminac. page 262 Standard times.(corected to September 2014)
List 1- PLACES FAST ON UTC (mainly those East Of Grenwich)
The times given bellow{ added to UTC to give Standard Time}
Should Be {subtracted to from Standard time to give UTC}
The List gives the hours with no sign
Page 264
Top List 11 Places Normally Keeping UTC.
Bottom
List 111- PLACES SLOW ON UTC (WEST OF GREENWICH)
The Times Given {Subtracted from UTC to Give Standard Time}
Bellow Should Be{added to Standard Time to give UTC}
The Places are listed without a sign
I did find on line a copy of a page from the Nautical Alminac listing Nautical Time Zones.
It is not in the current 2016 printed Nautical Alminac.
My copy is the Comercial Edition {bought at local Chandler)
Published By Paradise Cay Publications
Arcata CA
Copy right United Kingdom Hydrografic Office
If It Aint in the Alminac its Irrelevent.
Uricanejack
Well-known member
Well I had to look this up. I don’t like being wrong. So I have to find out the right answer.
History of Nautical time[edit]
Establishment[edit]
The establishment of nautical standard times, nautical standard time zones and the nautical date line were recommended by the Anglo-French Conference on Time-keeping at Sea in 1917. The conference recommended that the standard apply to all ships, both military and civilian. These zones were adopted by all major fleets between 1920 and 1925 but not by many independent merchant ships until World War II.
Letter Suffixes[edit]
Around 1950, a letter suffix was added to the zone description, assigning Z to the zero zone, and A–M (except J) to the east and N–Y to the west (J may be assigned to local time in non-nautical applications — zones M and Y have the same clock time but differ by 24 hours: a full day). These can be vocalized using the NATO phonetic alphabet which pronounces the letter Z as Zulu, leading to the use of the term "Zulu Time" for Greenwich Mean Time.
Zone Z runs from 7.5°W to 7.5°E longitude, while zone A runs from 7.5°E to 22.5°E longitude, etc.
These nautical letters have been added to some time zone maps, like the World Time Zone Map[1] published by Her Majesty's Nautical Almanac Office (NAO), which extended the letters by adding an asterisk (*), a dagger (†) or a dot (•) for areas that do not use a nautical time zone (areas that have a half-hour or quarter-hour offset, and areas that have an offset greater than 12 hours), and a section sign (§) for areas that do not have a legal standard time (the Greenland ice sheet and Antarctica). The United Kingdom specifies UTC−3 for the claimed British Antarctic Territory.
In maritime usage, GMT retains its historical meaning of UT1, the mean solar time at Greenwich. UTC, atomic time at Greenwich, is too inaccurate, differing by as much as 0.9 seconds from UT1, creating an error of 1⁄4 of a minute of longitude at all latitudes and which is 1⁄4 nautical mile (0.46 km; 0.29 mi) at the equator but less at higher latitudes, varying roughly by the cosine of the latitude. However, DUT can be added to UTC to correct it to within 50 milliseconds of UT1, reducing the error to only 20 metres (66 ft).[citation needed]
Modern Application[edit]
In practice, nautical times are used only for radio communication, etc. Aboard the ship, e.g. for scheduling work and meal times, the ship may use a suitable time of its own choosing. The captain is permitted to change his or her clocks at a chosen time following the ship's entry into another time zone, typically at midnight. Ships on long-distance passages change time zone on board in this fashion. On short passages the captain may not adjust clocks at all, even if they pass through different time zones, for example between the UK and continental Europe. Passenger ships often use both nautical and on-board time zones on signs. When referring to time tables and when communicating with land, the land time zone must be employed.
Usage[edit]
The nautical time zone system is an ideal form of the terrestrial time zone system for use on high seas. Under the system time changes are required for changes of longitude in one-hour steps. The one-hour step corresponds to a time zone width of 15° longitude. The 15° gore that is offset from GMT or UT1 (not UTC) by twelve hours is bisected by the nautical date line into two 7.5° gores that differ from GMT by ±12 hours. A nautical date line is implied but not explicitly drawn on time zone maps. It follows the 180th meridian except where it is interrupted by territorial waters adjacent to land, forming gaps: it is a pole-to-pole dashed line.[2]
Time on a ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, with negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and seconds for nations without an hourly offset). These signs are different from those given in the List of UTC time offsets because ships must obtain GMT from zone time, not zone time from GMT
History of Nautical time[edit]
Establishment[edit]
The establishment of nautical standard times, nautical standard time zones and the nautical date line were recommended by the Anglo-French Conference on Time-keeping at Sea in 1917. The conference recommended that the standard apply to all ships, both military and civilian. These zones were adopted by all major fleets between 1920 and 1925 but not by many independent merchant ships until World War II.
Letter Suffixes[edit]
Around 1950, a letter suffix was added to the zone description, assigning Z to the zero zone, and A–M (except J) to the east and N–Y to the west (J may be assigned to local time in non-nautical applications — zones M and Y have the same clock time but differ by 24 hours: a full day). These can be vocalized using the NATO phonetic alphabet which pronounces the letter Z as Zulu, leading to the use of the term "Zulu Time" for Greenwich Mean Time.
Zone Z runs from 7.5°W to 7.5°E longitude, while zone A runs from 7.5°E to 22.5°E longitude, etc.
These nautical letters have been added to some time zone maps, like the World Time Zone Map[1] published by Her Majesty's Nautical Almanac Office (NAO), which extended the letters by adding an asterisk (*), a dagger (†) or a dot (•) for areas that do not use a nautical time zone (areas that have a half-hour or quarter-hour offset, and areas that have an offset greater than 12 hours), and a section sign (§) for areas that do not have a legal standard time (the Greenland ice sheet and Antarctica). The United Kingdom specifies UTC−3 for the claimed British Antarctic Territory.
In maritime usage, GMT retains its historical meaning of UT1, the mean solar time at Greenwich. UTC, atomic time at Greenwich, is too inaccurate, differing by as much as 0.9 seconds from UT1, creating an error of 1⁄4 of a minute of longitude at all latitudes and which is 1⁄4 nautical mile (0.46 km; 0.29 mi) at the equator but less at higher latitudes, varying roughly by the cosine of the latitude. However, DUT can be added to UTC to correct it to within 50 milliseconds of UT1, reducing the error to only 20 metres (66 ft).[citation needed]
Modern Application[edit]
In practice, nautical times are used only for radio communication, etc. Aboard the ship, e.g. for scheduling work and meal times, the ship may use a suitable time of its own choosing. The captain is permitted to change his or her clocks at a chosen time following the ship's entry into another time zone, typically at midnight. Ships on long-distance passages change time zone on board in this fashion. On short passages the captain may not adjust clocks at all, even if they pass through different time zones, for example between the UK and continental Europe. Passenger ships often use both nautical and on-board time zones on signs. When referring to time tables and when communicating with land, the land time zone must be employed.
Usage[edit]
The nautical time zone system is an ideal form of the terrestrial time zone system for use on high seas. Under the system time changes are required for changes of longitude in one-hour steps. The one-hour step corresponds to a time zone width of 15° longitude. The 15° gore that is offset from GMT or UT1 (not UTC) by twelve hours is bisected by the nautical date line into two 7.5° gores that differ from GMT by ±12 hours. A nautical date line is implied but not explicitly drawn on time zone maps. It follows the 180th meridian except where it is interrupted by territorial waters adjacent to land, forming gaps: it is a pole-to-pole dashed line.[2]
Time on a ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, with negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and seconds for nations without an hourly offset). These signs are different from those given in the List of UTC time offsets because ships must obtain GMT from zone time, not zone time from GMT
davidej
Well-known member
Despite interjecting a couple of times, this is the first time I have read the thread right through.
In the end it is just a convention but it is not just forumites who can't agree.
Reeds quite unequivocally states that zones to the east of Greenwich are negative, While Wiki (and most of the zone maps I have seen) state that they are positive. In fact the Wiki on ISO 1861 (the time standard states the Berlin is +1. (This is a much better example then Paris, where the sun does NOT rise an hour earlier than Greenwich)
Could I respectfully suggest that Reeds has it all wrong and is confusing us.
If east is positive then we just add the number to UTC to get local time.. For my money, that makes much more sense
EDIT : I see Urricanejack has just contradicted his earlier opinion and posted the exact opposite
Confused? Moi? https://en.wikipedia.org/wiki/ISO_8601
In the end it is just a convention but it is not just forumites who can't agree.
Reeds quite unequivocally states that zones to the east of Greenwich are negative, While Wiki (and most of the zone maps I have seen) state that they are positive. In fact the Wiki on ISO 1861 (the time standard states the Berlin is +1. (This is a much better example then Paris, where the sun does NOT rise an hour earlier than Greenwich)
Could I respectfully suggest that Reeds has it all wrong and is confusing us.
If east is positive then we just add the number to UTC to get local time.. For my money, that makes much more sense
EDIT : I see Urricanejack has just contradicted his earlier opinion and posted the exact opposite
Confused? Moi? https://en.wikipedia.org/wiki/ISO_8601
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GHA
Well-known member
Reed does say "In the marine world " which tallys up with wiki entry on nautical time..
https://en.wikipedia.org/wiki/Nautical_time
Time on a ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, with negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and seconds for nations without an hourly offset). These signs are different from those given in the List of UTC time offsets because ships must obtain GMT from zone time, not zone time from GMT.
davidej
Well-known member
Which seems to suggest that sailors do it the opposite way to the other 7 billion people on the Earth
For instance look at this
http://www.timeanddate.com/time/map/
pmagowan
Well-known member
I am not saying there is a right or wrong. I am saying there is a logical way and a silly way of doing it
. You don't need to learn anything other than what a 4 year old kid knows to be able to subtract 1 from something else. If I write 2-1=? most people can work it out. If I write 2meters-1m most people can work that out even if they work in feet and inches. The fact that someone decided to go against logic a long time ago and a bunch of people have been taught to do it that way ever since does not make it a good idea. Personally I am all up for dumping tradition in favour of rational modernisation when it comes to this sort of thing. I could almost guarantee there are more people who get it wrong because of the current confusing system than get it right. That equals a system error!
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GHA
Well-known member
Does more than suggest......., your link isn't to nautical time zones.
From the HM nautical almanac office.
Like it or not, that's the way is at sea.
And in reeds
RichardS
N/A
Uricanejack
Well-known member
No I haven't changed my opinion, just acepted there is documentation showing it is an accepted convention for the naming of time zones east negative west posative by some people in some cicumstances. some of those people would appear to be the HM Nautical Alminac Office.
I am no longer blaming the Americans.
This is the British and French.
Uricanejack
Well-known member
Does more than suggest......., your link isn't to nautical time zones.
From the HM nautical almanac office.
Like it or not, that's the way is at sea.
And in reeds
Thanks for posting, I found this but couldn't figure out how to post.
Interesting point. Although this is from the HM Nautical Alminac Office. It is Not in the current 2016 Nautical Aliminac. At least not my copy. Reeds wouldn't know don't have a copy.
Interstingly I live in area U where most people insist Pacific Standard time is +8.
Dam I hate I hate having to admit I might be wrong.
GHA
Well-known member
But that doesn't mean it's not stupid.
Richard
Makes perfect sense to me, but that's how i learnt it.
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GHA
Well-known member
The same document is on the back cover of rapid sight reduction tables for navigation vol.2. Perhaps the others, that's the only volume I have.
So maybe the practice convention does come from celestial navigation, where it does make so much more sense to echo the hour angle conventions.
davidej
Well-known member
laika
Well-known member
Yay! Full Lakesailor!
GHA
Well-known member
Daydream believer
Well-known member
+1
Whenever I take the boat abroad with the family, I use British time. We all know British is best !!!!
Besides i do not know how to adjust my digital watch.
For tides I use Dover tide tables & non other
Mister E
Well-known member
I just hope that Wonga (other loan sharks are available) do not find out about this method of using the minus sign.
If the + and - were replaced with other symbols then this would avoid the confusion.