In the English dub, the Chunin exams are explicitly stated to begin on July 1st, making this the day of the written exam, and July 2nd the day the Forest of Death test begins, which lasted 5 days. Immediately upon that ending (on July 7th), they held a preliminary test of 1 on 1 combat, and upon its conclusion the hokage announced that the third test would begin in exactly one month, which would be August 7th. However when it shows Naruto's calendar, it has the 11th marked off as the big day and is showing a month which has 30 days while August has 31 days.