Here’s your primer on the rules of time travel in NBC’s ‘Timeless’

If you”re a time travel geek or a history buff, chances are you”ve been looking forward to NBC”s new contribution to turn-back-the-clock television, Timeless, premiering tonight.

Time travel is ultimately just a device for co-creators Eric Kripke (Supernatural) and Shawn Ryan (The Shield) to put iconic moments in history on screen and take their characters on a journey where they”re soon faced with questions of fate and identity. But it”s still a device that required some carefully crafted rules.

“It definitely makes me want to put a gun in my mouth, the rules of time travel,” Kripke told me at San Diego Comic-Con. “As we were beginning this show, all my friends who were writers on time travel shows were like, ‘How's it going?” and it seemed like they knew something I didn”t. I was like ‘What do you mean? It”s going to be fine.” By week 2 in the writers room, I was like, ‘Oh dear God.” The rules of where things change – it”s very, very hard to keep straight. But so far I think we”re keeping it reasonably under control.”

Kripke added that they “want Timeless to be a throwback to the Quantum Leap style of time travel.” Simple is the word both he and Ryan used for what they”re aiming for. “Mindf–ky” – as Kripke points out is the way many time travel shows and movies have gotten lately – is not the kind of entertainment they”re creating.

“We don't want the show – this is not meant to denigrate something – we don”t want to go deep into a rabbit hole like 12 Monkeys in terms of the time travel stuff,” Ryan said at a press event on the Sony lot last week.

Rufus (Malcolm Barrett), Wyatt (Matt Lanter), and Lucy (Abigail Spencer) step out of the time machine and into 1937 in the premiere of Timeless. Photo credit: Joe Lederer/NBC

As simple as they try to make it though, this is still a time travel show, so there are still rules to figure out that”ll give the writers headaches and will probably soon have the viewers debating for days on end.

So, whether you want a primer on the rules of Timeless so you”re not hitting the rewind button to make sure you”ve got them figured out while you”re watching the premiere tonight or if you”re checking out this post later and want a review, here is (a relatively spoiler-free) breakdown of what we learn about how time travel works from the first two episodes of Timeless.