Quote Originally Posted by zorro View Post
Is нa a preposition in Вадим старше меня нa год? In English I would think of it as "by one year". Why is it stressed unlike other prepositions? Are there other examples of this in Russian? Is there any underlying rule that might help me?
Actually any preposition that makes a syllable in its default form can be stressed. It was a norm long time ago but nowadays this kind of stressing mostly sounds archaic. So don't stress prepositions and you will be safe. But native speakers sometimes can pronounce preposition stressed and the following word completely unstressed.

Boris Petrovich promised us that he would come no later than two o'clock.
Борис Петрович пообещал нам, что он придёт не позже двух часов.
Борис Петрович пообещал, что придёт не позже двух.
Борис Петрович пообещал прийти не позже двух.
Борис Петрович обещал быть до двух.

Tell Vadim to be here at two thirty.
Скажи Вадиму, чтобы он здесь был в половине третьего. -ОК. Or "к половине третьего"