Carter states at the end of the episode that there is no way to know how much time passed. Actually, this isn't true, they can know the time. Very few planets were in the timeloop with them. They can go anywhere they were before the day the timeloop started. If there passed more than one day, that planet wasn't in the timeloop, so the time passed regularly there, and they can calculate the real time on Earth. Even more simple to ask their own teams, who were out somewhere else during the events (and couldn't come home).
When Jack is trying to convince Malikai to stop the device in the final loop, reflected in the sunglasses of Jack and Sam are the stage lights used. This light is not from the sun as the direction they are facing puts the sun behind them and no other lights are seen intentionally put there.
Although Jack's fruit loops are glued to the spoon for the breakfast scene (as mentioned in Notes), the people walking around in the background change every time events reoccur.
Trivia: P4X-639 was once a colony of the Ancients. They thrived there for thousands of years until they were struck with some sort of cataclysm or disease to which end they built a time machine to avoid their destruction. Instead of sending a team of scientists to the key moment of their history, the device caused a short term continuous loop. They experienced the same day, dozens perhaps thousands of times trying to get the machine to work but in the end they gave up, shut it down and let the end come.
Trivia: A total of 21 different time loops are seen during the episode.
When O'Neill was predicting when the Gate would activate and when it did, the computers in the background's screen still read "Idle" even though the Gate was active which then it should have changed from Idle.
Teal'c: It is powered by ionization.
Jack: In the atmosphere, right. Which is caused by... yut! (holds up finger) I know this one. Magnets!
Teal'c: The geomagnetic storm.
Hammond: So the loop can be broken?
Daniel: (walks over to the computer screen) Err... there's a section of text on the altar that deals specifically with the geomagnetic storms that power the device. Apparently, they recur every fifty or so years, which is why incidentally...
Jack: Yes, sir! The loop can be broken!
Daniel: If we really have had this conversation before, then I probably pointed it out to you that there's no way I can translate this entire text in less than a day.
Jack: I'm one step ahead of you... I put the whole thing on tape last time. So you don't have to start from scratch.
(Jack plays the tape; nothing but static. He rams it onto the side of the table, but to no avail)
Daniel: If what you say is true, then when the loop started again... your recording wouldn't have happened yet.
Jack: Yeah... right.
Teal'c: Did I not say your plan would be unsuccessful?
Jack: Careful! Be careful!
Sam: I'm gonna go run a few simulations.
(Sam walks away)
Jack: (to himself) You run. Simulate. Let me know how it turns out. Keep me posted. Keep me apprised.
(after the first loop, sitting in the commissary)
Jack: Weren't we just somewhere else?
Jack: Some planet.
Jack: Just now.
Jack: Ya sure?
Sam: It's a coronal mass emission. Like a solar flare.
Jack: But it's safe, right?
Sam: That's what this equipment is designed to find out. Apart from disrupting the planet's magnetic field, it might cause a significant increase in surface radiation.
Jack: But it's safe, right?
Jack: You know the worst part about this? Every time we loop Daniel asks me a question and...I wasn't listening the first time!
Hammond: Colonel what are you doing out of uniform?
Jack: Handing you my resignation.
Carter: You're resigning? What for?
Jack: So I can do...this!
(kisses Carter just as the time resets)
Jack: (hitting golfballs through the Stargate) How far is Alaris, anyway?
Teal'c: Several billion miles, O'Neill.
Jack: That's gotta be a record.
Hammond: What do you make of all this?
Sam: Well, sir, when was the last time you heard Colonel O'Neill use terms like "subspace field" and "geomagnetic storm"?
Hammond: Good point.
Sam: And he used them correctly... for the most part.
Jack: ...but I do know for a fact that there's no point letting ole' Doc Fraiser examine us again. (scene changes, the now familiar scene in the infirmary, with Fraiser yet again examining Jack's eyes) I ask you, what could possibly be in my eye that could explain this?
Jack: (suspecting Malikai) What kind of archaeologist carries a weapon?
Daniel: Umm...I do.
Jack: Bad example.
Jack: But what about Teal'c? C'mon, is this the face of a crazy man? (looks over at Teal'c) Bad example.
Jack: I'm telling you, Teal'c, if we don't find a way out of this soon, I'm going to lose it. "Lose it." It means go crazy. Nuts. Insane. Bonzo. No longer in possession of one's faculties. Three fries short of a happy meal. Wacko!!!
Hammond: Colonel O'Neill! What the hell are you doing?!?
Jack: (interrupting his golf shot) In the middle of my backswing?!?
Daniel: I realize that the Asgards returned [Jack] to normal, which is fortunate... I suppose...
Daniel: Anyway, I'm sorry but that just happens to be how I feel about it. What do you think?
Jack: Ask me tomorrow.
Jack: And you'll all believe me when SG-12 comes through that gate in 4..3..2..1.
(Nothing happens as everyone stares at Jack)
Hammond: SG-12 isn't due back for 3 days.
(Incoming traveler alarm goes off)
Technician: (over speakers) Unscheduled off world activation.
Jack: So close!
Sam: We haven't been to P4X-639.
Jack: Yes we have…(points at Daniel) No we haven't. That's what you were going to say.
Daniel: Of course that's what I was going to say.
Jack: Okay, bad example.
Jack: You know what they say, if at first you don't succeed, try, try, try, try, try, try again.
Jack: How would I know that?
Sam: Maybe you read my report?
Daniel: Maybe he read your report?!?
Jack O'Neill and Teal'c are shown juggling in this episode. According to several websites, Richard Dean Anderson worked as a juggler at one time.
Bill Nikolai (the technician O'Neill rides his bike past) also acts as Richard Dean Anderson's stunt double for the series.
In real life Christopher Judge plays golf and wants to join some ProAm tournaments.
The Fruit Loops on the spoon were actually glued there to make it look the same every day and in every shot.
This episode was featured in the Viewers' Favorites Stargate marathon aired by SciFi Channel during Labor Day weekend in 2005.
Director's cameo: Peter DeLuise can be seen twice, helping Daniel pick up his papers after he is knocked down by Sgt. Siler.
Syndication airdate: October 15, 2001.
In one scene Jack is reading a book called Latin for the Novice. The author is listed as Joseph Mallozzi, one of the episode's writers.
Jack and Teal'c are with Hammond in his office when there is an off world activation alarm. Jack says "D'oh" as they leave the office. "D'oh" is the catchphrase of Homer Simpson, from the animated series The Simpsons. Homer usually says this when he injures himself, of after he does something stupid.
Jack: Why? So you can be king of Groundhog Day?
Groundhog Day was a movie starring Bill Murray. In the movie Bill Murray's character got stuck in a time loop similar to what SG-1 was experiencing.