It was normally the Gunner officer who gave time when I was on exercise. This would ensure that any timings on a plan, notably H hour would be carefully co-oordinated with the guns firing. Any deviation could comprimise supprise, cause confusion or cause own casualties

Tine was critical to the bombardment plan in WW1 as poor communications meant flexibility was reduced (or non existent), so the rigid movment of barrage lines would take place at the designated times. If the infantry were slower than the timings, they could end up with no artillery support as fires moved away from them, too fast, and they would be shelled by their own guns.

A crtical point is knowing the time - it's time zone (yes I have seen this one scrwewd up) and it's designation ie 7 pm or 19:00 .

There have been a number of posts about time used in World War One.

Time Difference http://1914-1918.inv...time difference

Army Time http://1914-1918.inv...k

24 Hour Clock http://1914-1918.inv...k

What was the time in 1916 http://1914-1918.inv...k

This is my summary:

1914 - Time zone GMT timings --> denoted in AM / PM

1915 - Time zone GMT timings --> denoted in AM / PM

1916 - May 21 / 22 Daylight saving introduced timings -->denoted in AM / PM

1917 - Time zone GMT / Daylight saving -->denoted in AM / PM

1918 - Time zone GMT / Daylight saving -->denoted in AM / PM till 1st October 1918

AO 23 1918, effective midnight 30 Sep/1 Oct 1918 introduces 24 hour clock

1919 - Time zone GMT / Daylight saving --> deonted in 24 hour clock.

And from timeanddate.comthe dates for time changes for London can be found:

1914 No time changes

1915 No time changes

1916 Sunday, 21 May, 02:00 Sunday, 1 October, 03:00

1917 Sunday, 8 April, 02:00 Monday, 17 September, 03:00

1918 Sunday, 24 March, 02:00 Monday, 30 September, 03:00

1919 Sunday, 30 March, 02:00 Monday, 29 September, 03:00

All nicely presented in a diagram by eparges in this post - Time differences

timedifference.doc

Sources

From British Summer Time on the front thanks to Kevin for an entry from a war diary confirming daylight saving changes took place:

ALTERATION TO TIME. British Armies in France addopted summer time at 11pm this day and all clocks and watches

--------------------------------- were advanced one hour and so 11pm became midnight.

As ever thanks to Ron Clifton for clarification about when daylight saving was introduced and about time zone. From British Summer Time on the front

It is a common misconception that French time in WW1 (and in WW2) was one hour ahead of British. It wasn't - the British, French and Belgians were all in the Greenwich time zone. The Germans were one hour ahead. The French did not change their normal time until some date in the mid-1950s - possibly when the Common Market began in 1957.

Daylight Saving Time was introduced in 1916 and applied by all Western Front combatants, though not necessarily on the same dates. The actual dates are given in the Introductions to the British Official History, in the first volume for the relevant year.

The Armistice came into force at 11 am GMT on 11 November 1918.

A great contribution from Tony Lund in Army Time regarding the official introduction in 1916.

In May 1916 daylight saving time was introduced, and the Home Office sent out the following notice: “Important Alteration of Time. On the night of Saturday/Sunday, May 20 /21, at 2 a.m., the time on all railways, at all Post Offices, and other Government establishments, will be put forward by one hour to 3 a.m. The altered time will be used for all ordinary purposes during the summer. For instance, licenced houses, factories and workshops, and all other establishments where hours are regulated by law, will be required to observe the altered time.

“The Government requests the public to put forward all clocks and watches by one hour during the night of Saturday, May 20. Normal time will be restored at 2 a.m. on the night of Saturday/Sunday, September 30/October 1.

“The chief object of this measure at the present time is to reduce the number of hours during which artificial lighting is used in the evenings, and so save to the nation part of the fuel and oil used for lighting, and release large quantities of coal, which are urgently needed for other purposes arising from the war.”

Though a contribution from Time differenceby nigelS from an article in the Sunday Telegraph would suggest that there were proably a number of letters to the Times about it's introduction !

A slight deviation - Today's Sunday Telegraph carries a piece about the first changeover to BST on May 21st 1916 just four days after the "Summer Time Act" had received Royal assent on the 17th. There was, apparently, quite an outcry when this was drawn to the attention of the general public, with the editor of "Meteorological Magazine" calling it "Prussian Time" and "Sham time" while accusing the government of: "compelling us to keep the time of the enemy meridian". The Telegraph article continues by mentioning that a another correspondent was able to counter this allegation by pointing out that: "the fact that noon is now that of Berlin need not cause the patriot to shudder at the change, because in Germany and its subject lands the noon of Petrograd (St. Petersburg) is used to set the summer clock"; Germany itself having , apparently, introduced daylight saving during summer months so that its time corresponded with that of St. Petersburg in Russia. Although the military might not have been confused about the correct time, doubtless a large part of the general public would have been.

and Grumpy's library of Army Ordesr defines when 24 hour clock was introduced. Must have been interesting when that happened, one can almost here time being described as 23 o clock. From Army Time

AO 23 1918, effective midnight 30 Sep/1 Oct 1918.

Though the post by Hoplopfile from 24 hour clock idicates that the French were different !! (brings back memories of remember French army staffing procedures)

The French Army adopted the 24 hour clock just before the outbreak of the war, in 1912 or 1913

As well as the nice diagram eparges has summarised the methods adopted by the Allies and the Germans from Time Difference

looking for info on the difference between german time and allied time, I found several treads on this forum. Having applied some of the remarks, I found it didn't allways work or gave wrong results and did a little research. I found that:

* germans, french and brits introduced summertime in 1916

* german time was in general one hour ahead of european time

* allies on the western front (that is french and brits) used the french time

* all applied different dates for the beginning and ending of summertime

I 'poured' all this into a some tables (that is french and german times etc, since for battle(field)research the britishtime is irrelevant, hope I'm correct there, and postwar history didn't converse again..). Tables are german vs allied (french)

this gives for exemple:

* german source gives 12.00 (noon) on the 10th of may 1916, which makes it 10.00 am allied time

* allied source gives 20.00 pm on the 20th september 1918, which makes it...20.00 pm german time.

Well, hope I haven't made a mistake (or an ass), else, please correct!

Attached Files

timedifference.doc

german changes as for 1916,1917 & 1918:

30.04.1916, 23:00 Uhr - 01.10.1916, 01:00 Uhr

16.04.1917, 02:00 Uhr - 17.09.1917, 03:00 Uhr

15.04.1918, 02:00 Uhr - 16.09.1918, 03:00 Uhr