While I agree it is awkward, I cannot find a source that explains why. Merriam Webster contains one definition of the word "to" as being a preposition that is "used as a function word to indicate position or relation in time." This being said, I agree that it is awkward and would suggest using the word "and" instead.
On a side note, there are a few other elements of the sentence that add to its awkwardness. The most important one would be subject/verb agreement. The subject of this sentence, "office hours," is a plural noun. (Cambridge Dictionaries Online agrees with me). Therefore, the sentence should read "There are going" rather than "There is going."