Update grading-and-exams.md

Author: karkkieila

data/grading-and-exams.md

@@ -16,8 +16,8 @@ To pass the Python Programming MOOC courses you are expected to both complete ex
 * ~~Saturday 03.05.2025~~
 * ~~Saturday 07.06.2025~~
 * ~~Saturday 19.07.2025~~
-* Saturday 06.09.2025
-* Tuesday 21.10.2025
+* ~~Saturday 06.09.2025~~
+* Tuesday 28.10.2025 (New date!)
 * Saturday 22.11.2025
 * Saturday 17.01.2026