Vincent arrives at Alice's home on, according to her diary, August 3. The next day they go for a ride together and Alice writes about it in her diary. The date must be August 4, but her diary indicates (incorrectly) that it is August 5.
Outside of the "Mt. Kisco Playhouse" there are very tall mountains visible in the background but there are no mountains that size around Mt. Kisco, New York or anywhere a relatively short drive or train ride away from New York City.