1)
Why does the Torah mentions specifically overnight, a day and a night, two days a month and a year?
1.
Ramban #1 and Seforno: Refer to 9:17:2:1.
2.
Ramban #2: It may well be that the Torah mentions them because those were the actual time-periods - exclusively - that Yisrael encamped in the desert. 1
1
Ramban: Except for the nineteen years that they encamped in Kadesh, which the Torah hints here in Pasuk 19 "u've'Ha'arich he'Anan Al ha'Mishkan Yamim Rabim".
