He planned the date on Thursday and Friday.
The principle was the same one he applied to everything: work from what he knew about the person outward, and let the result follow. He knew Hermione. He knew what she found genuinely pleasurable as opposed to what she performed finding pleasurable, which were sometimes different things. She found bookshops pleasurable in the genuine way. She found good food pleasurable in the genuine way. She found being in places that had history and specificity — places that were not interchangeable with other places — pleasurable in the genuine way.
He also knew that she would find an over-planned, over-produced occasion slightly uncomfortable, because it would make her feel managed, which she disliked. The date needed to feel considered without feeling designed.
He sent a note to Honeydukes on Thursday asking them to hold a specific order. He made a reservation at Madam Puddifoot's — and then cancelled it, because Madam Puddifoot's was the wrong register entirely — and made instead a reservation at the back table of the Three Broomsticks, which had a window and was quiet in the early afternoon. He identified the route he wanted to take through Hogsmeade and the order of things.
On Friday evening Harry found him at the desk in the dormitory with a notebook open to a page of what appeared, from Harry's expression, to be a fairly detailed plan.
'It's a date,' Harry said. 'Not a military operation.'
'The principles are similar,' Ron said.
Harry looked at him for a moment. 'Is she going to like it?'
'Yes,' Ron said, with the specific certainty of someone who had been paying attention to a person for six months and trusted what he knew.
Harry sat on the edge of his bed. 'You've been thinking about this for a while.'
'Since January,' Ron said.
'Right,' Harry said. He had the expression he wore when he was deciding whether to say something. He decided. 'She puts your letters in her bookshelf. Not in a pile. On the shelf, between books.'
Ron absorbed this.
'I know,' he said, which was not entirely true but was close enough.
Harry went back to his book. Ron closed the notebook and went to bed with the readiness of someone who had prepared well for something and was simply waiting for it to happen.