The Admin > Business Rules > Triggers page contains a list of all of your account's active and inactive triggers, with a column for Last Updated. This allows you to see when a trigger was last edited, as well as sort by that attribute.
However, you may notice that a trigger or number of triggers carry a Last Updated timestamp that doesn't correspond to the last time you edited that trigger(s)... what's up with that?
Each trigger contains an attribute called "position", which defines the order that triggers fire (remember, they fire one at a time in order from top to bottom). This position attribute lives on the backend but is what's used to generate the order you see on your screen.
Creating a new trigger or repositioning an existing trigger can have a cascading effect on the position attribute for the rest of your existing triggers (both active and inactive).
Creating a new trigger and moving it up to the top of the trigger list means that the trigger with position: 1 now goes to position: 2, the trigger with position: 2 goes to position: 3, and so on and so forth.
Keep this in mind the next time it looks like some triggers were updated at unusual times - they may have just been making room for a new neighbor.