You are entitled to a compensation if your flight was cancelled and you were informed about the cancellation less than 14 days before the flight date.
In case if departure time of your flight was rescheduled to an earlier hour according to your reservation it is also considered as cancelled flight. In this case you are also entitled to a monetary compensation.
Based on the EU Regulation 261/2004 if the cancellation is caused by bad weather, strike or acts of terrorism the passengers are not entitled to a monetary compensation. Quite often airlines purposely mislead passengers about the reasons of the delays in order to avoid payment of monetary compensation.
If your flight is cancelled you have the right to choose between re-routing and reimbursement of the ticket price.
In case if you choose re-routing you have the right to: