Engage brain and hold on while we take a walk through what can only be described as a bug in Excel 2007.
The graph below is fairly simple and shows a 'dip' in some data - can you tell what month it is?
Did you say early February? Wrong. Obviously it is middle-January (the dip starts on 15 th January and lasts for a few days by February, it is back up to 'normal'. Surprised?
Well, here is a graph of the same data:
Quote clearly you can see that it is about the 15 th January - which is what the underlying data actually records. So how did that happen?
Have a look at the first graph again and check the months December, January, March, April. Well, where is February? The answer is that the graph's author wanted the graph to run from 30 December until 30 March with the axis marked every 1 month.
Microsoft Excel 2007 decides that, as February has only 28 days, it can't possibly display on the axis as it has been asked to start at the 30 th of the month. Don't believe me? The only change in the second graph was to set the start date of the graph to 28 th of December and, as before, mark the axis monthly. Note that the position of the data line does not move.
I could vaguely understand the following happened:
February is missed from the axis, but its 'space' is still there so that you don't misread the data line. Instead, the following occurs:
For some reason, February is missed and March moves to take it's place! Only problem is that the data line DOES NOT MOVE, so now you have the word March underneath February's data and April under March's data, etc, etc. We also have an extra entry (July in this example) even though the data doesn't run until July.
I could almost understand missing February when you tell it to mark the axis on the 30th of each month, but moving the axis without the data is silly.
Surely someone thought about how to handle months with less than 30 days? Maybe not!