From another site:
The HG entered the house on or around July 1st (photos of them at the FOTH arrived to us on July 2nd). They would have entered in the afternoon/evening, so a fair guess is 5pm (that gives plenty of time for the photos shot at the FOTH).
Apparently they entered on July 3rd at 8pm. That gives 4 hours for day one. Julie says "until 5pm this evening", so that's 17 hours for that day. In between were 28 more days in July, 31 in August, and 15 in September. That's 1776 hours.
That means:
4 hours (July 3rd)
+ 1776 hours (28 days + 31 days + 15 days... July 2nd - September 15th)
+ 17 hours (September 16th, day of HoH competition)
That makes 1797 hours total. Ivette guessed 1875, Janelle 1900. Ivette wins.
If you're counting from the first episode, which was on July 7th at 8pm, the total is:
4 hours (July 7th)
+ 1680 (July 8th - September 15th)
+ 17 hours (September 16th, day of HoH competition)
Total of 1701... not what Julie got.