The canon firmly establishes that ROTJ takes place one year after the events of TESB.
How?
Every bit of official information around says that in the Star Wars universe, TESB takes place 3 ABY (3 years after the Battle of Yavin), and ROTJ takes place 4 ABY.
Yeah I understand that.
My question was how does canon establish that as a fact?
Someone said it, is just not good enough. Or even if everybody says so is still not enough. There must a reasonable explanation, but this seems like just another urban legend became accepted fact, as the ‘fact’ that Owen Lars is a moisture farmer.