How is time manipulated in films?

How could you show 100 years have passed using only one set?
Focusing on one object, for example a countryside house, and showing small details changing around it. This could be a tree growing next to a house as we know they can take years to grow.
Another example could be, showing the house in a warm countryside setting, covered with flowers and looking tidy; then gradually letting it decay and become old, ruined and 'cold'.

How could you show a year has gone by?
The best example to show a year has gone by would be to show one clip and then the four seasons. For example, using the countryside house again, it could be shown with new dasies/dandilions, then the sun beaming on the house, followed by leaves falling from the trees and finally snow covering the roof and grass.

How could you show 24 hours have passed?
If the clip was showing a man sat in his chair in his house, you could have the moon go down, the sun come up and then the moon go down again. Another example could be zooming in on the clock and the hands quickly moving round to show us the time has passed.

How could you make it obvious that the next part of the narrative is a dream?
The screen could gradually become lighter so it's 'dream-like'. The outside of the screen usually becomes blurry to show it isn't what is actually happening right at that point and it's in someone's mind.