I woke up at 4:50 this morning with light in the window and birds singing. I'm thinking, June 22 is special, the longest day of the year? Don't want to miss that.
First light from my street looking north.
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How much morning had I already missed? I checked my daylight sensor which saw first light at 4:50 also. page 
Daylight sensor samples every five minutes.
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I had processed and plotted this data stream in the spring when we most often notice the days getting longer. Here we can compare recent summer days. page
Measured interval between dawn and dusk.
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Trigonometry tells us that change reaches zero on the longest day. Yes, today could be it. I also notice that summer days aren't as long this year. What's with that? Must be my backyard tree cove filling in more of the sky.