1) С 19 до 24 (..ого) августа..
можно выразить и таким образом:
2) С 19 по 24 (...ое) августа
Читая учебник, нашёл след. форму:
3) С 1994 по 1999 год...
is it the fact that they "count" the Xth yr in russian...like "I was born in the 1988th year" / ...1988-ом году [one by one translation]
while... I was born in february / в феврале
Considering the fact that years are kinda "collected" as shown above, the 3rd method in the book is true? That would be the only logical explanation for not using the genitive in 3)
Confirmation/Correction of my theory appreciated