>>29919708Judging by the supports (and especially the one on the roof in the back), those are probably conventional billboards, which have been around for I don't know how long. A long-ass time I'd imagine?
Electrical street lights have been around since the end of the 1800's, but we don't know if those are electrical or magical.
Cinema too has been around since the late 1800's. Note the lightbulbs used for decoration and letterboards for the movie's name. We're before neon, and use a physical letterboard rather than microchips and LEDs. The black board above the cinema sure looks weird though.
Manehattan in general is a turn of the century inspired post-industrialization city when it comes to fashion, architecture and style too. Year 1900 give or take a decade or two.
Of course, we can't look at the more fantastic places without clear real-world equivalents, like Canterlot, Cloudsdale or Crystal Empire, but another place that mirrors a specific period rather closely is Appleloosa, it wears it's "Wild West" influences on it's sleeves, so basically the second half of the 19th century.
Trains are 1800-onward, zeppelins are 1880-1940. Rarity's designs trend towards later Victorian fashion, maybe 1850-1890.
The biggest outlier I can think of is Las Pegasus, an obvious and clumsy parody of the Las Vegas strip in it's heyday. Although the technology used there isn't particularly advanced, and COULD be pulled off in the late 1800s, especially with magic, the attire, style, and inspiration for the place would place it as late as the 1970's.
Personally, I'd place Equestria as late 1800's with the occasional personal magical gizmo (Vinyl's table, Twilight's Science machine, Spider Squeezy Super Sleazy 9000, etc.) that does one specific task and is used by one person without any major impact on the setting, as well as a number of places where magic is superior to conventional technology (Cloudsdale, Canterlot), and just disregard Las Pegasus as an anomaly.
