The rumors are true! At least partially...
Fans have long speculated that the upcoming Wonder Woman movie will span through decades, starting with her origin story in Themyscira, continuing through World War I Britain and ending in our present day and age. The theory finally has some more meat on its bones as the newly released set photos reveal that Diana and Steve will indeed be in Britain during World War I. In one of the photos you can see a war propaganda poster in the background with the phrase "Your King and country needs you, enlist now." These posters were commonly seen in Britain between 1914 and 1918 to recruit soldiers for the war effort.
Check out the poster, surrounded by the British flag on the right
Here's Gal Gadot, decked out in World War I era garb
And Chris Pine as Steve Trevor
Additionally, there is a photo that shows a place where soldiers can exchange French currency, insinuating that they have come back from France, which means it is set at the end of the war.
It's an interesting revelation, as a World War I story deviates from the source material. Wonder Woman is immortal, but in the comics she is not brought to the world of mankind until World War II. It's not a big surprise that they are straying away from the comics, the movie would be too predictable if we already knew what was going to happen. It will definitely be interesting to hear more updates, and I for one am looking forward to its release in 2017.
You can see Gal Gadot portraying Wonder Woman in the upcoming Batman v Superman: Dawn of Justice on March 25, 2016.