This is where the location of the calendars are in order: There's 10 total, 2 specifically are in the good/bad endings.

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1/10 calendar is right outside your front door.
2/10 calendar is right outside the late students room.
3/10 calendar is found in the staircase.
4/10 calendar is found inside the painting room under the trashbag.
5/10 calendar is under the left yellow note on the right side after getting pass the chained up door.
6/10 calendar is in the bush right before getting into the taxi.
7/10 calendar is on the left side in the left tree outside of the university before you go in.
8/10 calendar is in the chain top right corner of the classroom before you go in.
9/10 calendar is in the umbrella rack near the front door in the bad ending.
10/10 calendar is under the test in the good ending.

Once you get all 10/10 calendars, you can get the "true ending", to get it you have to go back and try to save Him. (be warned, it's a timer fight).
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This is the code for the door in the university:
Stress=312433
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That's it :D ! Good luck :> ! Happy to help!
- Alms