Once upon a time, when my current Mess-in-Second-Draft-Progress was but an idea, I knew that I wanted to write about an unusual family. But because it was always going to be historical at heart, there was research involved. At the time, I did minimal Internet research--and then lined it up in an Excel file.
My aim was to write a romance novel and I wasn't sure how historical I wanted to get, so I basically entered in information on the Napoleonic wars, Waterloo, George III, what my characters were doing, anything I could find that I thought might be useful.
As you can see, it's pretty basic: year, month/date, location and a short description. The red means it's about a main character, the green a secondary character and black is historical background.
Doing that is how I realized that Miles, my protagonist, was born the same year as Napoleon, and was at the formative age of twelve when the American army won the Battle of Yorktown.
As I've continued and deepened my research, new events are added to the timeline. As the stories have developed, the timeline gets revised also.
Creating a timeline--whether electronic or visual--is one of the most basic things a historical author must do. There's no way that you're going to memorize everything in your time period. You may not be writing about those battles, but your characters may be talking about them or may know someone fighting in them. You don't want to be caught off-guard when they surprise you.
There's no better way to see how a battle in this year in this place could lead to a character being wounded or whatever plot twist is necessary.
I know some authors tape a visual timeline on their walls or bulletin boards to help them keep track of the period. Depending on how elaborate the plot or how large the scope is, I can see how seeing the events on a timeline concurrently can help.
Of course, a timeline is only a building block of the research. I'm currently reading about eighteenth century British society (it's a social history), after having read about the Regency era, after re-reading a book about British abolitionists, and having a handy reference book on the world of Jane Austen. But the timeline of the plot and the entire era as a whole is what keeps me grounded in this Georgian world I'm trying to translate from my head to the page.