The longer opening hours are part of the "CityArena Frankfurt", street festival in the city as part of the FIFA World Cup celebrations. Celebrations will also include gastronomic and cultural offerings from all nations competing in the World Cup . Also a "SkyArena" will light up the city's skyscapers.
During the World Cup shops will be able to open until 10pm from the 9th June until the 9th July (Mondays till Saturdays). On Sundays and the public holiday "Fronleichnam" (Corpus Christi) they will also be allowed to open between 2pm and 8pm. On the day of the Final (saturday 8th July) shops will be allowed to open until Midnight!
more information can be found on the website www.cityforum-profrankfurt.de

Picture (with permission): Lars P Mathiassen larscapes.com