If we want to get technical, the series is a "90s" cartoon with some overlap into the early 2000s. The series ended production in mid 2001. Yes, the show was done at Nick and Craig out of their studios by the time the big screen movie came out in 2002.
If this movie takes place "a year" after the series "ends", I would wager its timeframe to be 2002/2003-ish. Basically, early 2000s. Could even stretch it to 2004/2005. Before smartphones hit the market in 2007, and before they got really popular soon after.
Honestly, I know I am nit-picking details, but I am kind of annoyed the movie has smartphone technology in it. If you are an older fan, you get wrapped up in a bit of nostalgia watching the old episodes, and HA! works best as a show encased in the 90s and early 00s. Shoving a smartphone in it...like, completely takes me out of that time period the series is "supposed" to take place in. Honestly, why not just leave it at flip phones? Most of the fans who grew up with the show can relate to that.
I'm not too surprised at Helga having a laptop, as laptops have been around since the show began, and Bob has massive cash. As does Rhonda's parents and that other rich kid. Even Arnold had a desktop computer in his room back in the 1990s. But am I honestly supposed to believe that in this world, they have smartphone technology in the early 2000s?
This is a small reason as to why I wish this movie had been made earlier. If it had been released anywhere between 2009-2013, with two years of production behind it, the time gap wouldn't have been *as* influenced with technology. Instead, this movie comes out pushing into 2018 where kids Arnold's age mostly all have cell phones, easy mobile Internet access and texting apps. If this movie had kids dropping hashtags and updating their profiles, I would have flipped every table I could find.