I must say I'm kind of sceptic reading or writing anything on this particular day, but here it goes..
JAA: Regulation asks for "IFR time"...that's time following Instrument Flight Rules. for most of your flights that means when you are on a clearance (soemplaces you can fly IFR in G airspace without clearance, but let's not get in to that).
So when you go flying IFR you receive a clearance at startup and you follow it to your destination hence ALL block time is IFR, regardless of weather.
FAA: Regulation specifies "Instrument time" meaning time you spend with the instrumet as you reference. So if you go on a 5 hour trip with takeoff under IMC, cruise in VMC (above clouds for example) followed by an approach in IMC you logg the departure and the arrival as instrumet time, the rest just as "normal" time.
Most countries have similar regulations. It all comes down to what they are asking for.
I logg IFR time and Instrument time separately, to keep up with both sides....