Introduction
The DC Animated Universe timeline that I devised consists of past series such as Batman the Animated Series (including the Adventures of Batman and Robin and the New Batman Adventures), Superman the Animated Series, Batman Beyond, Zeta Project, Static Shock, Justice League and Justice League Unlimited, Justice League vs. The Fatal Five, and Justice League Infinity.
However, please note that this timeline is unofficial. That is, this timeline is created from my own personal observations and research. In order to make sure that this timeline maintains it consistency and validity, I had to incorporate many assumptions and constraints.
An assumption is easy enough to understand. I take a vague statement and add my own thoughts on what that means. For example, producer, Bruce Timm states that Batman was in his 30's after the end of the most current time in the present. I assume that the most current time is the final episode of Justice League Unlimited. With that year in mind, I calculate future years in the Batman Beyond era.
A constraint is something, in this case fact, that is binding and can not be modified. For example, in several episodes over the years, Batman is explicitly stated to be eight years old when his parents are murdered (recently, in an episode of Justice League named "a better world"). This fact is a constraint, and is used to calculate years in which he was born or other events such as the first year Bruce Wayne was Batman.
With that said, here is the Timeline.