A question about how time is kept in ships that travel across Atlantic.
When approximate time is mentioned in articles in this website, e.g.
'In the early morning of the 24th of May...',
I understand that this refers to the local time, i.e. the time that corresponds to that particular meridian.
When exact time is stated, e.g.
'...when at 0525 the Prinz Eugen's hydrophones...'
that 0525 is the local time, or GMT, or UTC or some other time reference ?
How the two fleets were keeping time?
Meridians & Time
I presume that costas is familiar with the concept of international time zones, so that an explanation of them is not necessary.
In the case of Prinz Eugen I would take it that the Germans were operating on Central European Time (the system they use today in conformity with the rest of the European Union) adjusted for the longtitudinal position of the ship into the relevant time zone.
The British I believe were operating on double summer time during WW2.
In the case of Prinz Eugen I would take it that the Germans were operating on Central European Time (the system they use today in conformity with the rest of the European Union) adjusted for the longtitudinal position of the ship into the relevant time zone.
The British I believe were operating on double summer time during WW2.
''Give me a Ping and one Ping only'' - Sean Connery.
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marcelo_malara
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There are three times that can be used at sea:
-GMT or Z (Zulu): needs no expanation.
-local time (or meridian time): this is the time for the EXACT longitude of the ship. This means that when the sun transits thru the meridian, it will be exactly 12 o´clock.
-zone time: this is the local time of the central meridian of the time zone extended 7.5 degrees west and east of it. This means that when the sun transits thru the meridian, it won´t be 12 o´clock (unless you are in the central meridian of the time zone).
I don´t think local time is used (unless you are heading dead N or S) because it would mean changing the time continously.
Using zone time would involve setting the clocks every 15 degrees of longitude change (780 nm at 30 degrees latitude for example). Or may be they set the clocks every two time zones crossed
-GMT or Z (Zulu): needs no expanation.
-local time (or meridian time): this is the time for the EXACT longitude of the ship. This means that when the sun transits thru the meridian, it will be exactly 12 o´clock.
-zone time: this is the local time of the central meridian of the time zone extended 7.5 degrees west and east of it. This means that when the sun transits thru the meridian, it won´t be 12 o´clock (unless you are in the central meridian of the time zone).
I don´t think local time is used (unless you are heading dead N or S) because it would mean changing the time continously.
Using zone time would involve setting the clocks every 15 degrees of longitude change (780 nm at 30 degrees latitude for example). Or may be they set the clocks every two time zones crossed
Thanks for your reply marcelo_malara.
I think it should be local time. (maybe I am wrong)
I would agree with you regarding meridians, longitudes etc (as far as maths is concerned) but there is a terminology and definitions. (wikipedia: time zone, nautical time zones)
I think it should be local time. (maybe I am wrong)
No; when the notion of time zones is considered, a time zone usually is referred to as the local time (wikipedia). So, local time isn't changed continuously....'I don´t think local time is used (unless you are heading dead N or S) because it would mean changing the time continously. '...
I would agree with you regarding meridians, longitudes etc (as far as maths is concerned) but there is a terminology and definitions. (wikipedia: time zone, nautical time zones)
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marcelo_malara
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The wiki does not give the definition of local time but redirects to zone time article.
From Bowditch (American Practical Navigator):
"Local mean time (LMT), like zone time, uses the mean sun as the celestial reference point. It differs from zone time in that the local meridian is used as the terrestrial reference, rather than a zone meridian. Thus, the local mean time at each meridian differs from every other meridian, the
difference being equal to the difference of longitude expressed in time units. At each zone meridian, including 0°, LMT and ZT are identical."
Strictly speaking, Local Time and Zone Time are not the same, despite the confused use of both terms.
From Bowditch (American Practical Navigator):
"Local mean time (LMT), like zone time, uses the mean sun as the celestial reference point. It differs from zone time in that the local meridian is used as the terrestrial reference, rather than a zone meridian. Thus, the local mean time at each meridian differs from every other meridian, the
difference being equal to the difference of longitude expressed in time units. At each zone meridian, including 0°, LMT and ZT are identical."
Strictly speaking, Local Time and Zone Time are not the same, despite the confused use of both terms.
I only know about US submarines, but we always used zulu time. That way the clocks never need to be changed and when you get a message that says something is supposed to happen at such and such a time there is never any confusion. If something happens at 0300 zulu in SE Asia, it also happened at 0300 zulu in New York City.
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marcelo_malara
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Yes, everything was done by zulu time including watch standing. Of course, in a submarine it isn't obvious when it's night or day in most parts of the ship.marcelo_malara wrote:Hi Bgile:
How did you do with the shifts? They started and finished al Zulu time?
I'm pretty sure surface ships do everything by zulu also, but I honestly can't be sure because I was never on one at sea. I know message traffic is always time-stamped in zulu time.
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José M. Rico
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Hello Bgile,
This is interesting because I know that midshipmen aboard the Spanish training school ship "Juan Sebastian de Elcano" on their instruction voyage around the world have to change the time continuously for daily duties such as watches. Of course, message traffic, entries on the ship's log, etc, are done by Zulu time.
Regards,
This is interesting because I know that midshipmen aboard the Spanish training school ship "Juan Sebastian de Elcano" on their instruction voyage around the world have to change the time continuously for daily duties such as watches. Of course, message traffic, entries on the ship's log, etc, are done by Zulu time.
Regards,
Hi Jose,
(sorry I don't know how to make the punctuation) ...
I would imagine that if a ship made a lot of port calls it would be much more convenient to always be on local time. Also, a surface ship's training evolutions are probably more dependant on the presence of daylight.
I can remember a six month deployment to the Western Pacific on which we spent a TOTAL of 28 days in port, and the average crewmember got ashore on 13 of those days. The rest of the time we were underweigh and most of that time we were submerged.
(sorry I don't know how to make the punctuation) ...
I would imagine that if a ship made a lot of port calls it would be much more convenient to always be on local time. Also, a surface ship's training evolutions are probably more dependant on the presence of daylight.
I can remember a six month deployment to the Western Pacific on which we spent a TOTAL of 28 days in port, and the average crewmember got ashore on 13 of those days. The rest of the time we were underweigh and most of that time we were submerged.
Time, clocks etc.
Finally I found out.
Definitions & preliminaries:
German Summer Time (G.S.T.) is ONE hour ahead of standard Central European Time. Central European Time is UTC+1
In his book, Baron Burkard chose to adopt German Summer Time since it was the same as the double British Summer Time used in the British ships and in all British accounts of the operation.
Also note: 'The clocks in the Bismarck were set on the Central European Time at noon of 23 May and remained so to the end.' (Baron-Burkard, Ch10)
Double British Summer Time is TWO hours ahead of GMT.
So, when in an article, (e.g. J. M. Rico's Operation Rheinuebung) time is mentioned, such as '...when at 0525 the Prinz Eugen's hydrophones...' the 0525 is double British Summer Time (=GST) ie 0325 GMT
Though stating exact time isn't important by itself, it is vital to mention its type, e.g. GST, GMT, local, etc. This helps a lot if you use programs (like World Wind) or maps to determine in which part of the 24hour the time refers, the position of the sun in horizon, shadows, etc.
I don't understand why the (reconstructed) Bismarck's War Diary uses G.S.T. instead of C.E.T.
Definitions & preliminaries:
German Summer Time (G.S.T.) is ONE hour ahead of standard Central European Time. Central European Time is UTC+1
In his book, Baron Burkard chose to adopt German Summer Time since it was the same as the double British Summer Time used in the British ships and in all British accounts of the operation.
Also note: 'The clocks in the Bismarck were set on the Central European Time at noon of 23 May and remained so to the end.' (Baron-Burkard, Ch10)
Double British Summer Time is TWO hours ahead of GMT.
So, when in an article, (e.g. J. M. Rico's Operation Rheinuebung) time is mentioned, such as '...when at 0525 the Prinz Eugen's hydrophones...' the 0525 is double British Summer Time (=GST) ie 0325 GMT
Though stating exact time isn't important by itself, it is vital to mention its type, e.g. GST, GMT, local, etc. This helps a lot if you use programs (like World Wind) or maps to determine in which part of the 24hour the time refers, the position of the sun in horizon, shadows, etc.
I don't understand why the (reconstructed) Bismarck's War Diary uses G.S.T. instead of C.E.T.