The bulk of the film take places over a period of five days, starting with Giselle meeting Edward and finishing with Edward and Nancy's wedding. This is borne out by both the screenplay and official novelisation.
Day 1 - Giselle meets Edward in the forest. They agree to marry the next day.
"Giselle! We shall be married in the morning!" the prince announced. ... [later] Giselle was so excited when she pulled up to the castle the next morning that she opened her carriage door rather quickly.
Day 2 - Giselle comes to the castle for her wedding and is pushed by a hag into a magical portal, leaving Andalasia (morning) arriving New York (evening). Robert rescues her and she spends the night in his apartment.
Robert waits on the phone. Despite his better judgement, he just can't bring himself to send her back out into the night.
DISPATCHER (O.S.) (cont'd): “Hello, sir. Destination please?”
But Robert doesn't answer, his eyes still on Giselle as he quietly clicks off the phone.
…
INT. ROBERT'S LIVING ROOM - MORNING
Giselle wakes with a demure sleepy stretch on the couch. Slowly batting her eyes awake, she looks around the room to realize... The home of her newfound friends is an untidy mess (the sloth of busy single parent)! Dirty clothes are strewn about, magazines litter the floor and the sink is full of dirty dishes.
Day 3 - Giselle makes a dress, sings in Central Park (and sends Ball tickets to Nancy with a verbal confirmation that the ball is tomorrow) and has a meal at an Italian restaurant.
"Yeah, usually you send those e-mail cards with the digital flowers. These are exquisite. Where do you find live doves in New York City?" Nancy cried. "And these?" she added, holding up a pair of golden tickets. "We're going to a ball?"
...
Robert smiled. Well, that was easy, he thought. "So, tomorrow night, then?"
Day 4 - Edward arrives at the apartment. Giselle and Edward have a date. Giselle buys clothes and they all meet at the ball later.
Day 5 - The scene at the end takes place the following day
The very next day, at the palace in the magical world of Andalasia, Prince Edward and Nancy were married. It was a royal ceremony, and everyone remarked that Nancy made a beautiful princess.
The very last scenes (Giselle taking over Nancy's studio, Pip and Nathaniel have writing and touring on their bestsellers) take place at an undisclosed point in the future.