The answer?partly depends on your definition?of a day hike.
About 5 years ago I did a day hike from Agnew Meadows to Shadow Lake to Garnet Lake to Thousand Island Lake and back?to Agnew.? This follows the JMT from a bit past Shadow Lake to Thousand Island Lake.? I think it was about 19 miles, so a long day (at least for me).? Very scenic.
If you return from Thousand Island to Angew via the High Trail, you get a bit of the PCT too (and an incredible view of the Minarets from a distance)
It was that hike that motivated me to transition?from a day hiker to a (novice) backpacker.
