This hike was definitely a challenge. It was a sunny  day. The temperature was in the low 60's when I began the hike at around 8:55 AM. and in it was 68 by 12:00PM.  It was below 80 after that. There were certain areas of the trail that had wind which helped to keep the weather sunny but cool. Other areas were warmer. My hike began at the Mitchell Cannyon Gate and began my hike clockwise using the following trails: Oak Road to Murchio (.33 mi), Culter Pine Trail to Bruce Lee Road (.43 mi), Eagle Peak Trail to Meridian Ridge Road (2.85 mi), Bruce Lee Road to Back Creek Trail (.23mi), Donner Canyon Road to Cardinet Oaks Road (1.46mi), Falls Trail to Middle Trail (1.24 mi), This section of the trail is rugged, very narrow, rocky and there is a lot of poison oak that sometimes stretch to the middle of the narrow trail, so you'll need to be careful. There is a lot of shade in this trail too, and water in the creek. The next trails are Middle Trail to Prospectors Road (.96 mi). From here, the trail gets a lot more steep. very few flat areas. The trail still narrow, lots of poison oak, but also lots of wild flowers. Lots of shade too.  Once in prospect road, there is little to no shade and it was warmer, it felt muggy and it becomes mores steep. It was a bit warmer but manageable do to the wind. Next, North Peak Trail to Summit Trail (1.02 mi) This is a narrow trail, there is partial shade but the last stretch is more exposed. Not as rugged and the middle trail. From here you can begin to see Mt Diablo Museum at the summit. The views from the mountain ranges in the East Bay are breath taking. The final stretch of the trail is from The Summit Trail to Mt. Diablo Summit (.45 mi).  The last stretch always seems a lot longer (at least to me).  Including several 10 to 15 minutes breaks from the beginning of the hike to the summit, it took me 6 hours to reach the summit. I arrived at the summit at 3:01 pm. I spent 45 to 50 minutes exploring the museum, eating my lunch and taking break. I got myself an ice cream sandwich an a cold gatorade at the museum store.  I was in heaven.  Then at 4PM I began my descent. I started via set Summit Trail to Juniper Trail (apron .25 mi), From here until the end, there will be a lot of downhill, some areas are steep. But not as steep as the Donner Canyon Road and the other trails going up. Then Juniper Trail to Juniper Campground (1.02 mi) lots of shade under the oak trees. Next, the Juniter Trail to Deer Flat Road (.20 mi).  This took me to the Then, Deer Flat Road to Mitchell Canyon Road (1.58 mi). This section is explored to the sun almost 100%. Once I reached the Mitchel Canyon Rd, It's 3.67 miles to the gate, where it all begun.  There is partial to no shade for at least half of the trail The last half a mile or so, is flat and it runs along the Michell Creek.  I reached the gate at 6:04:38PM.  I had a 2.5 litter water pouch in my back pack and came back with a little less than half left. But maybe because it was not too hot. So bring enough water. There are water fountains at the summit or along the creeks on both canyons so if you bring your water filter you can replenish as ofter as you want. However, I don't know if the creeks have water all year long. So it's best to be prepared.As challenging as this day hike is, I had a great time. I had a muscle tear in my  left cald two years ago and it still sensitive so strenuous hikes still bother it.  So, to avoid having another tear, I have to walk slower and take several short breaks of less long breaks Each rest break is at least 10 minute. But I still enjoy this hike. Lots of great views. Not a very crowded trail, but there is definitely enough foot traffic. I was alone form some time, but every now and then I would come across some other hiker. So the confusing part about the mileage and the time is that according to All Trails, I hiked 16.05 miles in 7 hours and 14 minutes. Even tough heir app indicates the trail is  14.40 miles and it should take an average of 8 hours and 5 minutes. But, according to the Map My Hike by Underarmor I did 15.59 miles in 8:33:20 minutes.  I asked the ranger which is correct and he said the route I followed is definitely closer to 16 miles. Alight I did see some birds and lizards, I was surprised that I did not see a single deer, squirrel or snake. I highly recommend this hike, you can do it as a day hike or backpack. Remember to wear sturdy hiking shoes. The rocky areas have sharp lose gravel/pebbles and one of them went through the sole of my hiking shoes and came back with a hole. Again, enjoy this awesome park whichever trail you follow. And please do not disturbe nature. leave plants alone. I saw some people taking flowers.