Unfortunately, this wasn't simply a Herculean task, but downright impossible. Aside from unavoidable contradictions between routes (e.g., the timing of Exams in Rin's route vs the others), some of the routes were in fact self-contradictory and work only in a conception of time beyond our comprehension (e.g., Lilly's route tries to cram something like 10 days between July 4 and July 10).
To some extent, you could argue this is the effect of an Unreliable Narrator. In fact, in Rin's route, Hisao states "I try to grasp the passing of time, but it seems hard. I'm still used to the rhythm of the hospital, where trivialities such as the day of the week or time of day didn't really matter. Everything was the same, no matter what. Rediscovering the significance of time is an oddly disorienting experience, and I find myself enjoying the fact that I can categorize events in this fashion."
This is a fancy way of leading into an important disclaimer: This is not an authoritative and canonical organisation of events, because such a thing is impossible. This is merely a "best attempt" to give all the events a specific day of occurrence while contradicting canon as little as possible.
Generally, timing was based on absolute dates first (e.g., Lilly's citation of specific days, Hanako's Birthday, the Marine Day three-day weekend), following the logical and officially stated remarks that KS takes place in 2007. The next place I checked was relative time references (e.g., the next day) and references to specific days of the week (If the last scene was on a Tuesday, and the next takes place on Monday, it means at least six days have passed. Due to the impossibility of some of the relative time references, I tried to at least honor Hisao's relative timing claims as either "one day" or "more than one day". Emphasis on "tried".
Finally, a note on Tanabata. Depending on where you are in Japan, it's celebrated anywhere from July 7 up through some time in mid-late August (one lunisolar calendar I found for 2007 places the "traditional" date for Tanabata at August 19). Only Lilly's and Shizune's routes care about Tanabata. In Lilly's route, Tanabata takes place after Hanako's birthday (July 10) and exams ("A couple weeks"). The implication is that Lilly leaves after classes and before Tanabata, but Shizune's route presents Tanabata as happening after exams and before the end of classes. As I stated elsewhere, my conclusion is that Lilly's too busy packing up her life to leave forever to be able to attend Tanabata, especially when her imminent departure would be placing a pall over the festivities. Ergo, I placed Tanabata at August 7 - a popular compromise between the Gregorian and Lunisolar reckonings.
For a detailed deep dive, I put together a shared Google Calendar, available HERE.
For a more user-friendly presentation, I put together some pretty color coded calendars for the most eventful months.
Lilly = Yellow
Hanako = Purple
Shizune = Blue
Rin = Red
Emi = Poplar
