(time conjunction) + past perfect continuous – English Grammar Profiler
In the English Grammar Profile, B2 point 67 in the category of PAST is defined as:
past perfect continuous after a time conjunction to give background information.
For example:
This was just a few months after Ebola had been terrifying the world.
listen
1 AFTER IT HAD BEEN SITTING 46
2 AFTER HE HAD BEEN DRINKING 29 3 AFTER I HAD BEEN USING 29 4 AFTER IT HAD BEEN RUNNING 28 5 AFTER I HAD BEEN WORKING 19
6 AFTER HE HAD BEEN MISSING 18
7 AFTER WE HAD BEEN DATING 16 8 AFTER I HAD BEEN PLAYING 14 9 AFTER I HAD BEEN TAKING 14 10 AFTER WE HAD BEEN TALKING 13 11 AFTER HE HAD BEEN WORKING 12 12 AFTER I HAD BEEN DRIVING 12 13 AFTER THEY HAD BEEN DRINKING 11 14 AFTER I HAD BEEN WAITING 10
15 AFTER SHE HAD BEEN MISSING 10
16 AFTER I HAD BEEN SITTING 9 17 AFTER IT HAD BEEN RAINING 9 18 AFTER I HAD BEEN LIVING 8 19 AFTER I HAD BEEN MAKING 8
20 AFTER SHE HAD BEEN DRINKING 8