Determination of the day of the week ISO 8601. The day designated with 7 may also be counted as "0", by applying the arithmetic modulo 7, which calculates the remainder of a number after division by 7. Thus, the number 7 is treated as 0, 8 as 1, 9 as 2, 18 as 4 and so on. If Sunday is counted as day 1, then 7 days later (i.e. day 8) is also a Sunday, and day 18 is the same as day 4, which is a Wednesday since this falls three days after Sunday. The basic approach of nearly all of the methods to calculate the
First day on the Somme the number of heavy guns increased from The new divisions needed supply trains a week to meet daily needs and a large number of extra trains, to transport heavy artillery ammunition. Until mid-June, ammunition supply for the BEF needed per week, then rose to per week, to deliver a stock of of munitions. Ammunition expenditure became a concern by 12 July but deliveries to the area behind the Fourth Army kept pace, although transport from railheads to the guns was not always maintained. In the weeks before 1 July, an extra seven trains a day were sufficient to deliver ammunition.