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This comic pokes fun at the idiosyncrasies of time keeping. Since units of time are intimately tied to a planet's rotation, and planets rotate at different, inconsistent rates, time keeping doesn't always follow a simple pattern.
Many stores advertise being open 24/7, which means that they're open all day, every day. Many locations of the convenience store chain 7-Eleven are now "open 24 hours", again meaning they are always open (despite historically being open only from 7 AM and 11 PM local time, hence its name).
The main joke in the comic refers to the fact that a day on Mars (the time it takes for Mars to make a full revolution on its own axis) is about 24 hours and 37 minutes of Earth time. If a 7-11 store is open for literally 24 Earth hours per Mars day, then it would actually be closed for around 37 minutes each day.
The first part of the title text refers to daylight saving time, where days can be shortened or lengthened on predefined days of the year in order to maximize use of available sunlight. In the United States, most places set clocks forward by one hour on the second Sunday of March, resulting in a 23-hour day, and back again on the first Sunday of November, resulting in a 25-hour days. Thus technically, even a 7-11 in the US would not truly be open "24 hours" every day. Arizona and Hawaii are called out as exceptions because they do not observe daylight saving time.
The second part of the title text refers to leap seconds, which are sometimes added to December 31 in order to synchronize time with Earth's actual rotation. Years with a leap second will see its last day being one second longer than 24 hours. Since leap seconds apply to all Earth-based clocks, any store on Earth that is open "24 hours" would technically have to close for one second.
Sign: 7-Eleven Open 24 hours
[A person in a spacesuit is trying to open the door to the convenience store]
Door: Rattle rattle
Caption: I'm glad they finally opened a 7-Eleven here on Mars, but it's annoying how it closes for 37 minutes every day.
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I don't think the title-text references leap seconds, as it says that "many" are wrong, not "all". It seems more likely it refers to stores that claim to be open 365 days per year, and are hence wrong in leap years.
184.108.40.206 20:12, 17 April 2017 (UTC)
I agree that it would be closed for 39 (and a bit) minutes a day if it was open for exactly 24 hours. I think Randall made a mistake. 220.127.116.11 21:30, 17 April 2017 (UTC)
The parts in the description that talk about mixing "Earth and Mars time units" and "Mars-hours" don't make sense; I'm pretty sure there's no such thing as a Mars-hour. Despite the classical definition of an hour (which has since been replaced), an hour is defined as a number of seconds, and seconds are an SI unit based on the characteristics of Caesium-133 atoms...NOT defined as being a fixed fraction of a day. Even the unit "day" is often used to refer to a fixed unit of time nowadays (defined by the SI to be 86 400 s)...I believe this is one of the reasons why the solar day on Mars is referred to as a "sol" instead of a "day". 18.104.22.168 22:15, 17 April 2017 (UTC)
- Nitpicking a bit, but the day is usually only 86400 seconds long (see 1481).
- That's what I meant to say, SI defines it to be 86 400 s; I have no idea why I typed 86 401 s. It is fixed now.22.214.171.124 15:39, 18 April 2017 (UTC)
- NASA's Mars Mission do divide the "sol" into 24 "Hours". I thought about adding this as a clarification the the Mars-Hours but that made the sentence somewhat unwieldy.126.96.36.199 09:27, 18 April 2017 (UTC)
Fun fact that might be interesting to add to the note about Arizona and DST. As stated already, the Navajo reservation observes DST, since it extends into Utah and New Mexico. However, the Hopi reservation, which is entirely enclosed by the Navajo reservation, does NOT follow DST. So in the one state in the Mountain Time Zone that does not observe DST, there is a region that follows DST, and inside that is another region that does not follow DST. 188.8.131.52 01:28, 18 April 2017 (UTC)
- And looking at a DST map of Arizona, it appears there is at least one small area contained within that inner-most non-observing region that does observe DST... 184.108.40.206 08:11, 18 April 2017 (UTC)
- Yes, it is a smaller Navajo area fully contained within the Hopi reservation, which is fully contained within the Navajo reservation, which is mostly contained within Arizona. 220.127.116.11 02:19, 21 April 2017 (UTC)
- Up through 2006, some of Indiana didn't observe DST. That really screwed with my college career, being from Virginia. Some of the time I'm on DST, others I'm not.
Another fun fact: Warning: can't unsee. Randall's representation of the 7-11 logo is inaccurate, as the 'n' in the real logo is always lowercase. 18.104.22.168 00:29, 25 April 2017 (UTC)
I think it is worth noting the irony of Randall's choice of 24-hour convenience store chain, 7-eleven, since it was originally re-named to convey extended --but not all day-- store hours; Randell declined to use Circle-K or the fictional Kwik-E-Mart either could have been chosen. --Graham Alig (talk) 15:14, 9 March 2019 (UTC)