1 during which time
She studied in China between 2000and 2003,DURING WHICH TIME her parents communicated with her by telephone.
2 by when / which time
He decided to work in this city in 2009,BY WHICH TIME / BY WHEN he had stayed here for 9 months.
3 about whose + noun
The Mayor himself attended our school meeting,ABOUT WHOSE presence the mass media talked a lot,speaking highly of his attention to school education.