I'll keep this brief, here my thoughts are more or less the same as with blue skies, but there's a couple other things that drag it down a star...
1. The beginning does not fit the mood of the rest of the song, it isn't a bad start, it just doesn't sound much like a song called "Summer Day"
2. A little too much of this song is uplifters, (by uplifters I mean transitional devices, stuff that's supposed to build up to a drop) they don't sound bad, but they're not supposed to take up much of a song and about half of this song has uplifters! Again, just like the volume jumping problem from Blue Skies, it's not jarring; but it's noticeable. It won't ruin the song, but it does distract me from it. I understand this is quite a short piece and I imagine that's the problem, so I would recommend in future to either cut down on the uplifters, or lengthen the piece to spread them out.
3. The drop, I'm sorry, but this is where everything just fell apart! Luckily it's short, but everything that is added to the mix at the drop ruins it... You seem to be pretty harsh on yourself with the detune, all of your songs except your second one are pretty good at balancing it and even your second one wasn't so bad, but here... It's fine until the drop, but then it just sounds like a mess of frequencies! It's not all too unpleasant, but it does take the flow and excitement out of the song, and disappoints after all the buildup.
That third reason's the real kicker, I would've still given this 4 or maybe 4.5 stars if the drop was fine, but it knocked you down to 3.5. I know I said I'd be quick, but when I start on one of my tangents, nothing can stop me...
Score: 73/100
P.S. 30-40 MINUTES!? That's believable, but still pretty damn fast for such nice sounding synths!