sutradan

1. the next day; the following day
   Stigli smo uveče, a sutradan smo išli na more. — We arrived in the evening, and the next day we went to the beach.
   Sutradan se nije ni setio šta je rekao. — The next day he didn't even remember what he'd said.

Don't confuse with sutra: sutradan means the day after the event described, usually in the past.