When Does the Film "The Devil Wears Prada" (2006) Take Place?
"The Devil Wears Prada" is a comedy film written by Aline Brosh McKenna that released June 30th, 2006. So when is "The Devil Wears Prada" set?
It takes place in the years:
We know this because about one-fifth into the movie Runway editor-in-chief Miranda Priestly explains, ..."in 2002, Oscar de la Renta did a collection of cerulean gowns." So it must be after 2002 AD.

2006 AD - 2007 AD
We know this because about one-fifth into the movie Runway editor-in-chief Miranda Priestly explains, ..."in 2002, Oscar de la Renta did a collection of cerulean gowns." So it must be after 2002 AD.
More specifically, during the next film, "The Devil Wears Prada 2" (2026), journalist Andrea "Andy" Sachs says, "So, I used to have your job!" and, then, "Yeah, back in... 2006." So at least part of the narrative takes place in 2006 AD, unless she is misremembering. Presumably, Andy is hired then, so the story starts in late 2006 AD.
Later, at the end of the infamous Harry Potter "unpublished manuscript" sequence, all three copies of the book Andy has made simply read "HARRY POTTER Book 7" on the front. The seventh book in the Harry Potter series, "Harry Potter and the Deathly Hallows" (2007), was released on July 21st, 2007 AD in the real world. So it must be before late July of 2007 AD. The real-world British writer J. K. Rowling reportedly finished the first draft of "Harry Potter and the Deathly Hallows" on January 11th, 2007 AD. So it must be after mid January of 2007 AD at this point.
Specifically, the climax takes place during Paris Fashion Week and at the start Emily Charlton specifically says, ..."I get to go to with her to Paris for Fashion Week in the fall." so it is probably fall of 2007 AD.
HOWEVER, during the Paris section of the tale Andy looks at her T-Mobile Sidekick II (first available on September 22nd, 2004 AD in the real world) and its screen displays "Dec 3" in the upper right-hand corner so presumably it is early December of 2007 AD at the end.
Additionally, there is an epilogue but it appears to be only days to weeks after the climax and therefore still in December of 2007 AD.
Quite early on, Andy says, "Dad, you have to trust me. Being Miranda's assistant opens a lot of doors. Emily is going to Paris with Miranda in a few months"... and the characters go to Paris only once so that must be the "Fashion Week" in "Paris" being referred to and the entire movie should take place in a matter of months in 2007 AD. Presumably, Andy is downplaying how long it is going to be to her father or she has misunderstood the fashion industry calendar this early into the job.

