Star Wars Voyager 1
Star Wars Voyager 1
[Cueball is looking down at the smartphone he is holding in one hand, while he is holding his other hand's finger up in the air. He is standing behind an armchair where Megan is sitting reading a book or paper. She holds it open with both hands. She has turned her head halfway towards him. Sitting on the floor in front of her is Beret Guy, legs bent and leaning back resting on one hand, with his phone in the other hand.] Cueball: The time it takes light to travel between Earth and Voyager 1 is exactly equal to the combined runtime of Star Wars episodes I-IX...
[A slim beat panel, showing only Cueball standing in the same pose as in the first panel.]
[Cueball looks up from his phone and raises his finger higher up. Megan has turned back to reading. Beret Guy looks up, and he has put his phone on the floor to put his, now free, hand on his heart, while singing, as indicated both with nodes before and after the lyrics he sings as well as letting his speech line start at a starburst near his head, rather than just beginning near the head, as normally.] Cueball: ... Now! Megan: Weird that I don't hear any fireworks. Beret Guy (singing): Should ollld acquaintance be forgooot

Cueball has added together all the runtimes of the Star Wars movies (episodes I-IX) and then calculated the exact time at which a message sent to Voyager 1 will have that exact duration in light speed delay. He announces this information to Megan and Beret Guy only seconds before it occurs, allowing him to signal the moment by saying "Now!", after waiting in the beat panel.
Megan expresses surprise that the event isn't being celebrated with fireworks. Judging by the fact that she doesn't look up from her book, her surprise is sarcastic. Beret Guy breaks into song with the New Year's traditional " Auld Lang Syne ".
This comic highlights an interesting relationship between the Star Wars Episodes and the NASA Space Probe "Voyager 1", which most likely no one else has thought about, but most likely fitting well with fans of both xkcd and Star Wars .
The original Star Wars film was released on May 25th, 1977, only four months before Voyager 1 was launched on September 5th, 1977. The last film was released more than 42.5 years later on December 20th, 2019, only three weeks before this comic.
Voyager 1 was, with a distance of 148.68 Astronomical units (22.2 billion km; 13.8 billion mi) from Earth as of December 26, 2019, the most distant human-made object from Earth. This data is given with reference in the Wikipedia article for Voyager 1. That was less than a week after the release of the new movie. That is approximately 20.6 light hours away. With the recently released last episode the total viewing time of the nine episodes is 20.35 hours (not including the spin-off movies). So a discrepancy of 15 minutes. This could be explained by the title text.
In the mission status of the two Voyager probes there were a One-Way Light Time of 20 hours 36 minutes and 46 seconds on the day the comic was released. This corresponds to 20.613 light hours, only the 46 seconds deviation from exactly 20.6 hours.
This is an odd coincidence that Cueball/ Randall saw significant enough to mark with a timer and acknowledgment to Megan and Beret Guy (and the rest of the fans of xkcd).
In the title text Randall notes that there can be different ways of measuring run times, both if you do not count credits into the runtime or with more than one version existing of at least the original trilogies films, with added extra footage. This means that if you choose the longest possible run time, you may still have a chance to throw a party for some time to come, as every extra minute of film will add time before Voyager 1 reaches that extra light minute.
However as demonstrated in the Table of runtime below, then only for the very longest versions would this have worked around the time of the release of the movie. Now, three weeks later it is too late.
When Voyager 1 left the heliosphere it was traveling at about 17 kilometers per second (11 mi/s), making it the fastest heliocentric recession speed of any spacecraft, and it is not really slowing down. (Do note that the speed with which it travels from Earth is not the same since Earth is in orbit around the Sun and sometimes travels faster towards Voyager 1 than Voyager 1 leaves the sun, but then Earth turns and goes the other way!)
Since a light minute is 1.799×10 7 kilometers it takes Voyager 1 12.25 days to travel this far. So for every minute added to the run time, the party start time will be delayed by more than 12 days. However, it is already 14 days since the distance given on Wikipedia, so more than one extra minute is needed to postpone the party to after the release day of the comic.
The last possible chance is to assume that all run times have been rounded down, which could add anywhere from a half a minute to almost 9 full minutes if they round 125.9 down to 125, and not only rounded 125.4 (and not rounding 125.5 up). Actually, assuming all runtimes are rounded down, it is realistic that there is on average half a minute extra runtime per episode making 4.5 minutes extra time. This would buy 55 extra days from the 26th of December... But to find this out correctly, someone would need to review all the 9 episodes from the very first second to the very last of the most extended versions. It seems that it could still be possible to find a day where the party can still be held after the release day of the comic.
In the extreme case that all movies went 59 seconds over a full minute, but all times are rounded down, it would add 8 minutes and 51 seconds. This could give 108 extra days from 2019-12-26, meaning that Easter Sunday 2020 (2020-04-12) would be the last possible day for such a party.
This may also be a play on the confusion between the Star Wars and the Star Trek franchises. In the case of Star Trek, the very first movie dealt with a Voyager probe (Voyager 6 in this case), and the number of hours and quantity of Star Trek movies rivals and exceeds that of the main Star Wars movies; about 25 and a half hours between 13 movies.  Maybe we'll see this in an xkcd when Voyager gets a little further away?
[Cueball is looking down at the smartphone he is holding in one hand, while he is holding his other hand's finger up in the air. He is standing behind an armchair where Megan is sitting reading a book or paper. She holds it open with both hands. She has turned her head halfway towards him. Sitting on the floor in front of her is Beret Guy, legs bent and leaning back resting on one hand, with his phone in the other hand.] Cueball: The time it takes light to travel between Earth and Voyager 1 is exactly equal to the combined runtime of Star Wars episodes I-IX...
[A slim beat panel, showing only Cueball standing in the same pose as in the first panel.]
[Cueball looks up from his phone and raises his finger higher up. Megan has turned back to reading. Beret Guy looks up, and he has put his phone on the floor to put his, now free, hand on his heart, while singing, as indicated both with nodes before and after the lyrics he sings as well as letting his speech line start at a starburst near his head, rather than just beginning near the head, as normally.] Cueball: ... Now! Megan: Weird that I don't hear any fireworks. Beret Guy (singing): Should ollld acquaintance be forgooot
