The Nova Scotia Archives recently posted some "then and now" aerial photos. It looks to me like the new ones are 2018 and the old ones are early to mid 1930's. They do not exactly line up (this would be pretty challenging for an aerial) but they are pretty close.
The north side of downtown
A modern view that extends south an extra block or two
South End ocean terminals area. Probably Queen Mary?
Far North End, showing the area that was devastated by the Halifax Explosion
A much wider shot
There are many more aerials here:
https://www.flickr.com/photos/nsarchives/