sredinom

1. (of time, + gen.) in the middle of; in mid-
   Platu obično dobijam sredinom meseca. — I usually get my salary in the middle of the month.
   Vratiću se sredinom sledeće nedelje. — I'll be back in the middle of next week.
2. (of place, + gen.) down the middle of; along the middle of
   Pijan je išao sredinom ulice. — Drunk, he was walking down the middle of the street.

Used with the genitive: sredinom godine, sredinom leta.