Google and Julian

I’m reading Google Hacks, by Tara Clishain (of ResearchBuzz) and Rael Dornfest, and enjoying, if not always understanding, it. There’s a bunch of interesting things about simply searching Google that I didn’t know, let alone the main business of how to create special search tools with Perl scripts etc. I’ll take care not to pepper you with my ignorance-reduction moments as I work my way through the book, never fear; but I can’t resist passing on a thing or two.

For example: when imposing a date range on your Google search you must use Julian days.

Now I know what you’re thinking. Well, no I don’t, but you may be thinking that because Google rules the known world, so to speak, it’s tight with the original Caesar and has adopted his slightly wonky calendar scheme. Nope. The Julian in question was Julius Caesar Scaliger (how’s that for a bathetic name?), father to one Joseph Justus Scaliger who, to reconcile all the various dating schemes in historical documents, invented his own method of keeping time and honoured his dad in the bargain.http://www.geocities.com/calendopaedia/julian.htm He counted days, starting with noon on January 1, 4713 BC. (Don’t ask. It had something to do with the co-incidence of various solar and other cycles.)

You may not be surprised to know that some 2.5 million days have passed since that starting gun — 2453720 as of today, to be exact. That’s today’s Julian day. I learned this courtesy of a pair of online converters, one supplied by the U.S. Naval Observatory (because it’s really astronomers who groove on this Julian thing — apart from Google, that is), and the other out of our own McMaster University.

Google and the date range? Oh, yes. Not as interesting as the digression perhaps. The dates in question are the dates Google indexed the site, of course, which may be some time after the page was created or modified — and if it’s a page that gets re-visited, the date may keep changing. But you can use it to exclude pages indexed prior to a particular time. For example, this search slaw daterange:2453000-2453544 gets pages from wayback up until just about the time Slaw started — and no results at all from Slaw, of course. Other than that, I’ve found the results to be a bit unreliable. But you give it a whirl and let me know what use you make of it, if any.