I'd guess it's either 1890-1920, 1750-1820 or 1100-1150.

dats a lot of guesses

Ok I'll help you out. The map is based on a strategic boardgame that even has its own map here on warlight.net . It's very popular in France and the first letter of the game is a z.

Zebras eat polar bears?

I just conducted a search through all the WarLight maps that have a 'Z' in, but I couldn't find any that begin with that letter.

Edited 8/31/2015 01:12:54

Interesting, looks a little compact but if you can pull it off you ae on to a good one!

https://www.warlight.net/Play?PreviewMap=44434

Cities have inner cities or castles while bordered by other cities which haven't. Also , the surrounding of a big city should be negative.

Nobody still realised that 10,15,30 stands for 10 armies per turn , 15 armies per turn and 30 armies per turn?

^^^ I definitely associated the numbers with income...

But when people said that the income didn't correlate exactly with the current populations of the cities, I think you lost a lot of guessers. :)

( I wasn't even in the hunt for guessing, and my local time right now has nothing to do with it.)

It does look like a very cool map though. :)

'It would seem Manchester for instance is marked green despite being only the 9th most populated city in the UK... I'm leaning more towards area of each city? '

Where the heck did you get this fact from?
Manchester is the 3rd largest city in the UK.
I presume that the city values also take political significance into account (making capitals and the such more valuable) as well as balance.
Also, 10, 15 and 30 are very high values for individual territories, especially considering how many cities are depicted in the map.

Edited 9/1/2015 14:13:08

KAAAAA (like a bird i suppose)

also i couldn't find 2.