Google is constantly updating and tinkering with its search algorithms, and most of the time we never notice. The service is a black box, and what goes on inside is anybody's guess.
But I've noticed something in the last week that's going to affect the way I type queries. About a decade ago (cripes), I picked up the habit from Robot Wisdom, the granddaddy of all blogs, of searching for a phrase by typing periods between the words instead of the more common way of surrounding the phrase with quotation marks. It's much easier to touch-type
"three one two"
especially when you're searching for two phrases at once, which I sometimes do when I'm looking up lyrics, bits of dialogue, or something I remember from a news article. Typing quotation marks requires pressing shift and moving your hands, but periods are easy. And until very recently, the results were identical.
This no doubt exploited some quirk of Google's punctuation handling, and I can see that there aren't many people who do this, so the side effect was bound to disappear at some point. I'm just surprised it has lasted this long. I'm sure this latest change includes lots of invisible improvements that we'll all grow accustomed to without realizing it, so I won't complain that this now produces different results from this.
Time to retrain my fingers.