... at least 30 mins after official sunset .....
Ah, that reminds me! Must revalidate my night rating, as soon as the clocks go back.
Pre JAR, it used to be 5 solo circuits, in anything with any number of engines, & then you were valid for the next 13 months for both SEP & MEP.
Now, assuming that you have already done the 3 T/O & land in last 30 days in daylight, in each class, all you need is one solo circuit in a single, and one solo circuit in a twin.
BUT, on the other hand, even if you have not flown at night, at all for say the last year, you can toddle off in the dark, in any SEP or MEP, so long as you do not take a passenger.
Now, that is logical, Mr Spock ....