Standard Time; is it just me that had it wrong?

[richardbrennan]

Whilst idly reading this months YM, an article about how to pass the RYA Offshore shore based course caught my eye, particularly the section on time zones.

I must admit that if anybody asked me what the standard time was in Cherbourg I would have happily have said GMT or UT plus one. However, it appears I am wrong and checking in Reeds confirms this as the standard time is annotated UT minus one, i.e. what you have to do to the standard time in Cherbourg to get to UT. Having met a couple of sailing mates for lunch, it would appear that they have been making the same mistake for years as well!

Of course in practice it really does not matter as long as the correction is made the correct way, but I now realise that the time zone and the standard time appear to be two different things!

 

[RichardS]

When I did my Yachtmaster classroom at college a few years ago I would say that this single issue caused more confusion amongst we students than any other matter we studied during the 1 year course.

We could all understand True / Variation / Magnetic / Deviation / Course but we all found UT-1 a bitch to grasp!

Richard

 

[Buck Turgidson]

I had the same brain fade when I did the YM course. Ive been using timezones in aviation my entire adult life but this -/+ annotation in the marine world just confused the hell out of me. In the end I just ignore it and use what I know.

 

[FWB]

I had the same encounter with Neville Featherstone when he used that notation in one of his books.
I think it was the Yachtsmans Almanac...I ditched it. I wrote to the publishers about what I thought was an error.
He sent me a snotty email telling me how wrong I was and what a great chap he was. Must have had it wrong for all my years as an Airline Pilot.
I think the poor chap may have sadly passed away now though.

 

[BERT T]

Let me confuse it a little more:

GMT is a time zone officially used in some European and African countries. The time can be displayed using both the 24-hour format (0 - 24) or the 12-hour format (1 - 12 am/pm)

UTC is not a time zone, but a time standard that is the basis for civil time and time zones worldwide. This means that no country or territory officially uses UTC as a local time.

 

[lpdsn]

Let me confuse it a little more:

The good news is that everyone is right. The ISO standard has it as UTC+1 for CET (in Winter anyway).

Whereas...

https://en.wikisource.org/wiki/The_American_Practical_Navigator/Chapter_18#1806._Zone_Time

Or is it everyone is wrong...

 

[GrahamM376]

I also remember it confusing but, no longer. I just download tide tables (mobile geographics) in local time so no amending necessary.

 

[marklucas]

It's simple really.

The time at your location (timezone) is linked to UTC by the simple formula UTC + X (where X can be postive or negative). This gives you the simple fact of what factor would you have to add to your location time to get to UTC.

As an example, Cherbourg (CET) is currently one hour ahead of UTC and is it's time is written as UTC-1 i.e. I have to add -1 one hour from my local time to reach UTC. I live on the East Coast of the USA and so am in UTC+5 e.g. EST.

Obviously summer time mucks things around, but that is the principle. What do I have to add to my local time to get UTC. This is certainly the sense in which it is used in tide tables / navigation (unless you are the RN and they just stick to Zulu time).

 

[richardbrennan]

I am glad it's not just me; I was an airline pilot as well before I retired, obviously it adds to the confusion!

 

[Cantata]

This has always confused me and it's useful to read the explanation.
However it's somewhat a*se about face IMHO. Surely it would have been more logical to say e.g. that Paris time is one hour ahead of UTC i.e. it is on UTC+1, instead of which it's defined as a zone where you subtract 1 to get UTC., so actually UTC-1. Makes no sense at all.

 

[Lon nan Gruagach]

Wiki has it that for Nautical Standard Time you calculate UTC(1) by adding the offset to local time and for Standard Time you calculate local time by adding the offset to UTC
https://en.wikipedia.org/wiki/Nautical_time
https://en.wikipedia.org/wiki/Standard_time

Is it really acceptable to assume the context?

 

[GHA]

However it's somewhat a*se about face IMHO. Surely it would have been more logical to say e.g. that Paris time is one hour ahead of UTC i.e. it is on UTC+1, instead of which it's defined as a zone where you subtract 1 to get UTC., so actually UTC-1. Makes no sense at all.

Have to disagree, the sun rises in Paris an hour before it does in London (or thereabouts) utc - 1. It's just the clocks going the other way doesn't make immediately intuitive sense,

 

[RichardS]

This has always confused me and it's useful to read the explanation.
However it's somewhat a*se about face IMHO. Surely it would have been more logical to say e.g. that Paris time is one hour ahead of UTC i.e. it is on UTC+1, instead of which it's defined as a zone where you subtract 1 to get UTC., so actually UTC-1. Makes no sense at all.

Totally agree. On my RYA course we all made the same point to our excellent tutor but, as he said, he doesn't make the rules ... just teaches them! We had to understand it to pass the exam but he also assured us not to worry about it as in the real world of the cruising sailor it won't be a big deal.

And after 8 years in the Med I can state that he was right!

Richard

 

[laika]

Nautical Time Zones (see wikipedia link in Dougal Tolan's post #11) aren't described in the same way as civil time offsets. An old chart was linked to in a previous post but here's a recent one from the UKHO:
http://astro.ukho.gov.uk/nao/miscellanea/WMTZ/Wmtz150918.pdf
The blurb describes the naming rationale. Per Dougal Tolan's post, you get local standard time by subtracting the zone from UT. Minus a minus is a plus. Yes possibly confusing but +numbers going left and -numbers going right from the prime meridian makes some sort of aesthetic sense.

 

[Uricanejack]

To hell with UTC use GMT.

Mathmaticaly
Everything East or north is on the posative side of the axis
Everything West or south is on the negative side of the axis

When I learned Navigation, GMT was Mathematicaly correct. So was the D.O.T. appears the RYA and perhalps the MCA have lost the plot. I blame the UN

 

[westernman]

My computer thinks that Paris is UTC+1.

Surely as UTC is the universal reference, then everything else should be referenced to that. So the time now in Paris is UTC+1.

 

[laika]

The Problem is UTC is Amercican

Umm..it isn't. If it was American, or indeed British, it would be called "CUT". If it had been all up to the french it would have been "TUC". It ended up as UTC...

EDIT: wikipedia link on "UTC" etymology:
https://en.wikipedia.org/wiki/Coordinated_Universal_Time#Etymology

 

[pmagowan]

This has always confused me and it's useful to read the explanation.
However it's somewhat a*se about face IMHO. Surely it would have been more logical to say e.g. that Paris time is one hour ahead of UTC i.e. it is on UTC+1, instead of which it's defined as a zone where you subtract 1 to get UTC., so actually UTC-1. Makes no sense at all.

I agree. If Paris is UTC-1 and it is 10 oclock at Greenwich then it is 9 oclock at paris! 10-1=9 unless maths has suddenly changed. Nobody writes a mathmatical formula inversely! 10-1 does not equal 11!

 

[Buck Turgidson]

Wiki has it that for Nautical Standard Time you calculate UTC(1) by adding the offset to local time and for Standard Time you calculate local time by adding the offset to UTC
https://en.wikipedia.org/wiki/Nautical_time
https://en.wikipedia.org/wiki/Standard_time




Is it really acceptable to assume the context?

I'm not sure calculating a Universal constant from a local offset is how it's supposed to work. I think there is probably a reason for using a universal constant and as such all local times should be derived from it.

 

[Daedelus]

I agree. If Paris is UTC-1 and it is 10 oclock at Greenwich then it is 9 oclock at paris! 10-1=9 unless maths has suddenly changed. Nobody writes a mathmatical formula inversely! 10-1 does not equal 11!

Only nearly - look at the time in Paris (let's say 9 0'oclock) then to get to UTC look at the time zone : UTC-1, so subtract 1 from the time to get UTC. Therefore it is 8 o'clock UTC.

I think it is done so that the simple minded can work out UTC from wherever they are - they don't need to think - since it is -1 they simply subtract one from local time to get UTC.



I have the vague recollection of reading somewhere that UTC and GMT differ by some miniscule amount of one second, but so little that for all practical purposes it makes no difference.