s-Genitive and/or of?
There is no strict rule when we use 's and when the of-phrase.
1. s-Genitive – mostly for people and animals
Ronny's bike
the cat's basket
2. of-phrase – mostly for things
the name of the school
the top floor of the building
If things have a connection to people we also use the s-genitive (possessive).
Germany's economy = the ecomony of Germany
In time expressions we also use the s-genitive (possessive).
a three weeks' holiday