The very premise of the film is faulty.  We are introduced to a character named Rufus (George Carlin) living in a utopian society in San Dimas, California, seven hundred years in the future, in 2688.  This world is based on the music of Wyld Stallyns, a band formed by the movie's main characters, Bill S. Preston, Esquire (Alex Winter) and Ted Theodore Logan (Keanu Reeves).  But, according to Rufus, that won't happen if the boys fail history, and they are about to fail if they cannot get an outstanding grade on a history report.  If they fail, Ted will be sent to military academy in Alaska, and the band will never exist.

If you've been following this web site, you already see the problem.  But let me present the problem for those just joining the discussion on this page.  Our understanding of time requires that causes must exist sequentially before their effects, even if they are displaced temporally due to time travel.  This means that there must be an original timeline, a history, running from 1988 to 2688 before Rufus can travel back to 1988.  But according to the premise, if Rufus does not make that trip, Wyld Stallyns will be just another obscure garage band, and the entire society based upon their music will never exist.  Thus we have the problem that Rufus won't make the trip unless he makes the trip--he causes his own history.  This is the reverse form of the grandfather paradox, the inevitability problem:  if you appear in the past, you are destined to depart from the future.  (For those paying attention to alternative time travel theories, this is insoluble in the dimension-hopping view, although it does work in the fixed timeline theory, because all actions by everyone are inevitable.  This film may be an argument for the fixed timeline theory, but our discussions will be focused on unraveling it based on the theories presented on this site; we discuss the problems with the fixed timeline view in several places, most notably in The Science of Time Travel.)

Is it possible that without Rufus' intervention Bill and Ted might pass history anyway, or that failing history might still form the band at the right time and do what must be done?  If this were so, Rufus would have no cause to make his trip, as the utopian society would have come into existence without his action.  But everything we know about 1988 goes against that possibility:  Bill and Ted are about to fail history; they not only don't know the answers to their history problems, they don't even understand the questions; and Ted's father is already gleefully making arrangements to ship him to his new school.  No, there must be an original timeline AB in which the boys fail, Ted leaves, the band never forms, and the utopian society of the future does not come to pass.  But in that case, Wyld Stallyns is less than a footnote in history, and there is no reason for Rufus to make his trip to correct what he could not imagine.

Yet with a bit of extrapolation, the premise is salvageable.  Perhaps someone, probably someone named Rufus, made a trip back in time from the original 2688 (point B) to 1988 (point C, as history is inherently altered by his presence), and there encountered Bill and Ted.  Not for a moment imagining that the grades of two dim-witted high school students on a history report could be of any significance whatever, he assists them in his C-D timeline with an introduction to real history.  The details of this are the purest conjecture.  If he gives them control of a time machine akin to the one we see in the film, it is likely that they will have adventures much the same as those we are about to unravel.  On the other hand, he could take them on a sane, orderly trip through time, changing nothing of consequence, and creating a simple N-jump before 1988.  However it happens, Bill and Ted are inspired to produce an A+ report, pass history, and go on to form their band.  All of history from that point forward is altered, bringing about the utopian society.  And the revered published biographies of Bill S. Preston, Esquire, and Ted Theodore Logan tell of the strange visitor from 2688 who changed their lives completely.  Thus the rulers in 2688 have had time (seven hundred years) to determine who went back and what they did, and so to make an effort to intentionally confirm what was done accidentally in the C-D timeline, sending Rufus back from point D to create the E-F timeline.  It is this history which we see as the film begins.

From a time analysis angle, the first important point we are given is that Ted's father, local police chief, has lost his keys.  This becomes important later, and we will have to deal with it at that point.  The first time travel event is the trip Rufus takes from 2688 to 1988.  But nothing is simple in this film, because this anomaly is about to give birth to an entire series of internal anomalies.  But even before they begin, we have another complication, as Bill and Ted arrive from their own future, and tell their younger selves to trust Rufus.  It's a small problem.  Obviously the first time these events happened, the counterpart travelers could not arrive because they had not yet begun the trip; but Bill and Ted are faced with a problem--their pending report--and Rufus has offered to help, so they would probably begin the trip anyway.  Once the timeline unravels properly, they will appear to themselves, and the final history will have them meeting in both points of time.  But on the first trip, no mention has been made of the princesses, and Ted has not been reminded to wind his watch.

The design of the time machine owes something to Dr. Who, as it looks like a phone booth, but with a complex antenna on top.  The explanation of how time travel works is kept simple and improbable, written off with a "modern technology" excuse.  This is not about how time travel itself works, and clearly does not intend to address that idea.

But they then create the next anomaly, traveling back to 1805 to see Napoleon's invasion of Austria.  Napoleon orders them destroyed, and they flee back to their time machine and head for the future.  However, Napoleon is thrown by the blast of his own cannon into the path of the active time machine, and apparently (and inexplicably) dragged along to 1988.  This creates a very strange circumstance, as it means that at this moment Napoleon Bonaparte vanished from history (probably listed as "killed in an 1805 explosion") fairly early in his campaign to conquer the world; yet he is still a known historic figure, whose contribution to the history report will remain significant.  In a moment, Ted will leave the dictator in the care of his little brother Deacon, who will subsequently abandon him at a bowling alley leading to a wild collection of events which have nothing to do with our time travel story save that the Napoleon who is returned to 1805 will be a rather different person from the one who left that time.

At this moment, something occurs the interpretation of which has some impact on our understanding of the time events:  Rufus steps into the time machine and leaves, and another time machine immediately arrives.  The question which faces us is whether this is one event, or two.  If the time machine leaves, and another is sent from the future, then an entire seven hundred year history must be lived, in which our characters have only Napoleon (who is never returned to his place in history in this version), so that the moment when the second time machine leaves the future can occur.  However, if we instead understand this as the time machine duplicating itself in the present as it departs for the future, we are still part of the same E-F timeline.  In the first case, Bill and Ted will do their history project with the help of Napoleon, and presumably get the required grade (otherwise the future is undone) and then another time machine is sent back for them to use to improve their grade (a foolish choice on the part of those in the future--if their first foray into the past was successful, another trip runs a serious risk of causing a disaster); in the second case, our story continues immediately, as the boys again travel to the past.

It is also at this point that they introduce a fiction which makes no sense at all:  "The clock in San Dimas is always running."  Unlike Marty McFly, who observed that he had a time machine and therefore all the time in the world, Bill and Ted have only the amount of time between now and the time of their report.  But more on this later, as well.

The boys then begin hopping around through time creating temporal anomalies left and right.  In each case in which they remove someone from history they cause that person to mysteriously vanish from the world, never to be seen again before their report.  (In theory, they later replace these people, so they will return to existence never to have been missed.  In that subsequent timeline a similar report will be made, and the history of those people will be much as we know it.)

Their first stop is 1879, where they remove Billy the Kid from history.  This creates an immediate change in history (the disappearance of a notorious outlaw), and time must advance through all of the events until Bill and Ted leave to get Billy the Kid.  But these events will be confirmed, because the adventurers will still go to 1879 and take Billy.

Next they move to 410 BC, and take Socrates.  This sets up another anomaly, a new timeline in which the previous anomalies (removal of Napoleon and Billy) are contained.  The effects of this would be much like the removal of the Kid, but there are a few quirks which interrupt this.

The first quirk is their stop in the fifteenth century.  Here they meet a couple of princesses, but leave them behind.  Despite what Rufus will say later, these two young ladies will be forced to marry those old noblemen in several histories before they are rescued.  But there is no anomaly caused this time; Bill and Ted created a new history when they took Socrates, but in stopping here they have only become part of this history.  Since the history in which Socrates disappears is still being created, they become part of it the first time through.

But the next event is not so benign.  The foursome now travels to 2688, the origin of the time machine, and see their benefactors.  Normally a trip to the future does not create a problem; but in this case it is a disaster.  This time, it is Bill and Ted themselves who vanish from history never to be seen again; and since the entire world of 2688 is based on their as-yet-unrecorded music, they no longer exist and will never send Rufus back with the time machine.  Although it is internally complex, it resolves to an infinity loop spanning from 410 BC to 2688 AD.  At this point, we revert to the CD timeline, in which a traveler named Rufus happens to help two high school students with a report, and history remains forever trapped here.

But the film still has some interesting points to make, so we'll ignore this problem and continue with the story.

At this point it becomes a game of how many historic figures can you cram into a phone booth.  They create a string of anomalies running into oblivion (they can't have left from 2688, so they cannot have created any of these; but in overlooking that we would suggest that we have a string of similarly disastrous anomalies each terminating in 2688).  First they pull Sigmund Freud from 1901 (creating a new timeline), then Ludwig von Beethoven from 1810 (another timeline in which the Sigmund Freud and Billy the Kid anomalies are repeated), then Joan of Arc from 1429 (a new history in which all previous anomalies except Socrates are repeated), then Genghis Khan from 1209 (another).  They then pick up Abraham Lincoln from 1863, the first of these which does not become the beginning of a new history (it is part of the same history in which Genghis Khan vanished).  They then leap backwards, creating an alternate history spanning from one million BC to 2688 AD and repeating all the intricate anomalies already created.

Jerry-rigging repairs to their time machine, they leap forward to San Dimas, and at this point alter their earlier history by appearing and talking to themselves.  Ted realizes that he forgot to wind his watch, and they solve the problem of why they can't seem to reach home in the morning.  But this begs the question, why can't they just stay here overnight?  The movie wants us to think that if they don't reach San Dimas in the morning, they won't be there in time for their report.  But if they stay in San Dimas tonight, why won't they still be there tomorrow when it's time for the report?  The theory fails.  But, following his advice, they hop forward with their crowd of people, arriving on the morrow two hours before report time.  They now have really two problems.  One is that their report must suggest what these people think of San Dimas in the twentieth century, so they have to see some of it; the other is that Napoleon has disappeared.  But these problems are only remotely connected to our time travel questions (our historical figures will be very different when they return home).  Suffice it that they do recover Napoleon, but in the process lose the rest of the crew who are arrested by Ted's dad for disrupting things at the mall.  In order to do their report, they have to spring their project from prison--and this is where the really interesting ideas start to appear.

Bill and Ted introduce us to this idea:  if they agree to do something in the future which involves changing the past, will those changes be effected in the present?  My answer is yes and no; but we'll take it one step at a time.

Bill and Ted realize that to get their companions out they will need keys.  They resolve to travel back in time and steal Ted's dad's keys (you remember that they had disappeared) and hide them behind the sign in front of the police station.  But they haven't done this yet, so the keys aren't there.  All is not lost--they still have Napoleon, and can talk about the others that they met to some degree, so they leave and go get an A on their project.  But since they still have to restore all of the important people to history (remember, Lincoln's assassination never happened now) they still have to arrange the breakout.  So this time they go back and take the keys, hiding them behind the sign, and creating an anomaly which should resolve to an N-jump (since they will make the trip next time to confirm that the keys are behind the sign).

This raise the issue of the keys.  Where were they in that original timeline?  There are two good possibilities.  The first is that Ted's dad genuinely lost his keys somewhere else, but then Ted traveled back and stole them before they were lost.  The second is that the keys were never lost in the original timeline, but that we never saw that history--in the history we know, Ted had already come from the future and removed the keys.

But there are more obstacles to cover.  Once inside, they realize they need a distraction.  They don't have one, but they concoct the idea of using the tape recorder on a timer.  It doesn't happen, they go back and do their report with Napoleon, and this time when they travel back to get the keys they also set up the tape.  Maybe they also leave a note for themselves on a typewriter by an unoccupied desk, but this is unlikely.  On the next time through this history, they pick up the keys and the recorder activates on schedule, and in they go--but they get caught going by an unoccupied desk, and never complete the plan.  Back to the Napoleon report, and back to the past, and this time add the note (or possibly add the word "duck" to it).  On the next timeline they find the keys, the tape, and the note, and make it into the jail.

Well, this is very iffy at this point.  Maybe they get out of the jail; maybe Bill does the report while Ted sits in jail, but they get an "A" on the project.  Maybe Ted happens to make it out through the window and get the report going before his dad catches them.  Maybe they convince dad that they need these people for their history report, or maybe they leave and do the report again with just Napoleon.  Whatever happens, they agree that the trashcan idea Ted had at the moment of crisis was a good idea, and on their next trip back they install it.  Now everything works, and they do the report with a full contingent of historic figures.

The story is not yet over.  Bill and Ted still must return their new friends to their right places in history.  If they do it right (returning Socrates first, then Genghis Khan, Joan of Arc, Napoleon, Beethoven, Lincoln, Billy the Kid, and Freud), they create a single anomaly in which everyone returns to his place in history.  If they do it exactly wrong, each of those returns is another anomaly, a new history running from its point in the past to 1988.  But we are not told how they do it.

One thing is clear, however:  they don't take these people back until after they have taken care of their alterations to the police station.  To do otherwise would be to risk all that they achieved, to create an infinity loop in which the last leg is that they failed to rig the jail and had to go through it all again.

Rufus then appears at their band practice with two guitars and two princesses.  His independent travels create additional interacting anomalies, but since we don't know when they fit we haven't covered them.  We do know that he takes the princesses from history; but if we assume first that their marriages to the elderly noblemen never produced any offspring and second that those same noblemen would not have otherwise altered the human population (e.g., having children or preventing someone else from doing so), it's a simple N-jump.

He asks for Bill & Ted's autographs, and for permission to jam with them.  Neither of these events will significantly alter history.  The delivery of the guitars might make some difference; but I'm one of those who thinks that talent and creativity are more important than equipment, and if the duo shows promise they'll succeed with what they have and get decent instruments eventually.

If you're on your toes and a fan of the film, you'll have noticed that I failed to mention Rufus getting the autographs of the princesses, who after all he says were also in the band.  That's because they weren't, and then he didn't know they were; there was a previous history in which Rufus did not bring the princesses (or the guitars, unless he's been hanging around the twentieth century waiting for this moment).  When he brought the princesses, it was because he knew that the boys were taken with them and wished to help them during their journeys.  At that point Wyld Stallyns did not have two fifteenth century princesses on vocals.  But it sets up a new anomaly, as Bill and Ted include their "babes" in the band, Rufus becomes aware of this, and in the next timeline also requests their autographs knowing that they were part of the music.

And that concludes their excellent adventure; but they still had a bogus journey to make; and there are a few quirks there, too.