If we get super hot weather this summer, watering may need to happen every 4 days, and you may need 2 inches. You can measure how much water is coming out of your sprinkler system, or just check your soil profile. Dig down 12 inches. You want all 12 inches to be moist so the roots grow that deep. Yes, Kentucky bluegrass roots can grow that deep, they usually don't because of incorrect watering. (Caliche can also stop roots, and if that's your situation, it's tough to grow anything).
Twelve inches is also good for your trees, since their roots only go 12-16 inches underground. When you starve your soil profile of water using the 3 times a week for 20 minutes method, you're also starving your trees.
In between waterings, the top portions of soil and roots will dry out and that's exactly what you want. Then load up on water again so the entire profile is damp. Controversial? I don't really think so, but some argue about it because it doesn't "feel right" to water only once a week.
Now, I know folks will also say they've watered that way for years and their lawn looks fine. Mine looked fine, too. But the point is that more treatment is needed to keep problems away (like billbugs and thatch build-up) and far more water is used. Using the once-a-week method means about 40 percent less water is used during the season.
Also, be careful about doing Internet research on lawn care. Most of the information isn't written for our zone and climate.
There are some companies selling automatic systems now, mostly for commercial landscaping, that include soil moisture probes installed about 10 inches into the profile, and the sprinklers will run only when needed.
A lot of research has been done on this topic, and if you want to read more, I recommend, "Scotts Lawns: Your Guide to a Beautiful Yard." It also includes details on the proper fertilizing schedule for Kentucky bluegrass, and it's not the one most service companies provide.
Wishing you a green, lush lawn this summer!