Well reading from the above answer reminds me of one similar flight I had. It was a flight from Zurich to London. Flight leaves at 07.05 and arrives London at 07.55 (50 minutes) but if you do it the other way round flight leaves London 07.05 and arrives Zurich at 09.55 (almost 3 hours). It is a very similar case between the flight from Belfast to Prague. Actually the flight takes only 2.5 hour. Flight leaves Belfast at 07.00 (GMT +0) and arrive in Prague at 10.25 am (GMT +1). This explains why return flight from Prague to Belfast is shorter in time.

 Flights from Belfast to Prague take different lengths of time according to airline and route. The main carrier to Prague from the Northern Ireland airport is Jet 2, whose flights can take between three and three and a half hours. A flight leaving Belfast at 07.00 would arrive in Prague at 10.25am. Return flights are shorter, usually taking about one hour and a half. These flights cost £99 on average.