No time period in particular, however the setting within the cities will be Magi-tech based, so think of a somewhat futuristic society that has slightly more advanced technology then modern day humans. Which revolves around magic as its source of power. So older tech that operates off of other sources of power is still a possibility if desired, but the world is more of a cross blend between fantasy and sci-fi, as magic plays a pretty big part, but the weapons and such are a blend of swords, bows, staves, guns, etc. Either with magic blended in, or just regular tech blended in if that makes any sense. Sort of like the world of Fire Force, but instead of everything being powered by the eternal first flame, it is powered by magic, so the world contains a lot of older things, but also a lot of more futuristic things at the same time. 


As far as skater stuff is concerned, I don't see that being an issue, it is a fantasy/sci-fi type of world so a skateboard wouldn't be out of the question and I see no issues with it personally.