For flight planning must the forecast weather be above minima one hour before, after or at ETA? (EU-OPS)
Weather above planning minima one hour before and after ETA for flight planning and for determining alternate requirements (2 alternates vs 1).
Weather above planning minima at ETA for commencing flight. 
Weather above operating minima at ETA for continuing flight.


One way you can think of it: in the cockpit weather at ETA. In the briefing room weather one hour before and after.