Croatia is still not part of the Schengen area. The border between Croatia and, say, Slovenia or Hungary is treated as an external border and you should get an exit stamp, which also means the time spent in Croatia will not count towards the 90-day maximum stay in the Schengen area.

In practice, the fact that Croatia is bound to join the Schengen area means it has to implement similar rules and show it can perform border controls up to a certain standard. But even if it is actually ready next year, there will be some time before it becomes part of the Schengen area (“full implementation of the Schengen acquis” in the lingo).

Note that Romania and Bulgaria were supposed to join at the beginning of 2014 and were deemed ready by the European Commission but their entry was still blocked by other member states so it's not clear what will happen after Croatia officially applies.

Croatia is still not part of the Schengen area. The border between Croatia and, say, Slovenia or Hungary is treated as an external border and you should get an exit stamp, which also means the time spent in Croatia will not count towards the 90-day maximum stay in the Schengen area. Same thing if you take a flight out of a Schengen country to Croatia. Just like flights to the UK, they leave from the non-Schengen part of the airport.

In practice, the fact that Croatia is bound to join the Schengen area means it has to implement similar rules and show it can perform border controls up to a certain standard. But even if it is ready next year, there will be some time before it actually becomes part of the Schengen area (“fully implements the Schengen acquis” in the lingo).

Note that Romania and Bulgaria were supposed to join at the beginning of 2014 and were deemed ready by the European Commission but their entry was still blocked by other member states so it's not clear what will happen after Croatia officially applies.