The sources, principally are:
http://www.greatwar.co.uk/ particularly the "timeline" pages, which give a brief listing on what they think the major events are. It's a good starting place, but they do tend to miss a significant number of what other people consider to be "major".
http://www.rafmuseum.org.uk/researc...ine/interactive -aviation-timeline.aspx Again, the most useful pages on the site are the timeline; but they of course, tend to focus on the air war, and again, miss a number of events that don't directly involvespecifically British Military Aviation. The anniversary of the death of Oswald Boelcke, for example, isn't mentioned at all.
http://www.firstworldwar.com/onthisday/1914_08_05.htm has a day-to-day calendar, and give a great amount of detail that others often miss; but one of the weaknesses of this site is that it is positively jingoistic at times.
https://twitter.com/centuryagotoday is an excellent site for much of the non-warfare, political/social events that I list. This is also the original page that leads me into the side forays into imgur.
Finally,
http://ww2-weapons.com/ which used to be labelled World War One .net, is a great supplemental source; often providing excellent details, on the level of the third listed reference, but with significantly less bias.
...and of course, there are occasional other sources I quote or link to, like the dreaded wikipedia; also, I've picked up a considerable amount of my own background knowledge over the years from some many different places, I can't possibly remember them.