1905. No World War I. The Victorian Age is remembered as a golden age.
The timeline is good enough that I recognize the pre-1905 dates from our history and the post-1905 dates don't make me go, "Nah, that just wouldn't work." This doesn't mean someone with more historical background or even familiarity with Britain wouldn't snicker, but it passed the basic test for me.
And, hey -- Tesla! Zeppelins! Battle corsets!
Also perpetually ash-filled air, constant zombie attacks, spreading blight and famine, and seriously exploited underclass.