Even if 607 had been the actual date of the destruction of Jerusalem .... 1914 would still be wrong. Why?
When the WTS says that "7 times" equals 2 x 3,5 times of Revelation = 2 x 1260 days = 2520 days > one day / one year rule = 2520 years.
Now, 2520 / 7 times means that one "time" has 360 "days". This corresponds to the LUNAR year. So, to calculate the lenght of the "7 times", the WTS used LUNAR years (360 days on each). However, to apply those 7 times into the actual calendar to determine on what year they would finish, the WTS used SOLAR years of 365 days! Do you see the inconsistency?
Now, what would happen if we would be CONSISTENT and calculate the time interval using the same rule, using LUNAR years? Would we arrive to 1914? No, we wouldn't.
Indulge me on this one. If we were to convert lunar years in solar years, how much would that be? A lunar year = 360 days. A solar year = 365,25 days (the added 0,25 is to cover the leap years). That means that, for every LUNAR year in the calendar there's a difference of -5,25 days in relation to the SOLAR year. Now how much difference is that after 2520 LUNAR years? 2520 x 5,25 = -13230 days. if you then divide this number by 365,25 you get the difference in SOLAR years towards the LUNAR years. The result is -36,221, or minus 36 years, 2 months and 20 days, give or take.
This means that instead of calculating 2520 LUNAR years into a SOLAR year calendar, the WTS should have converted lunar years into solar years first. Then 2520 would effectively become 2483 years, 7 months and 10 days, give or take. Let's just assume the 10 days as an interval of tolerance.
Now, lets re-calculate (WTS style): From Tammuz (June/July) 607 AEC to December 31st 1 AEC = 605 years and 5/6 months. Now 2483 years and 7 months minus 605 years and 5/6 months = July / August 1878. So, even assuming that the WTS had the date of 607 BCE as the correct date for the conquest of Jerusalem by Nebuchadnezzar, the correct "end of the gentile times" would have been 1878 and not 1914.
[For the sake of comparison, let's make the same calculation having as sarting point the date generally accepted by scholars as the accurate date for the destruction of Jerulalem: 587 BCE. And let's do the same calculation. From Tammuz (June/July) 587 BCE to 31st December 1 BCE: 586 years and 5/6 months; Now, 2483 years and 7 months minus 587 years and 5/6 months. = July / August 1896.]
So, has anything relevant thing happened in 1878? Or in 1896? [By the way, just on a curious note, if you would consider the year zero as one extra year, you would arrive to ... July 1879, the month when Zion's Watchtower began to be published.]