So let me pose this questions. Using only the Star Wars films, describe for me the physical shape of a Nerf that would be herded by "Scruffy-looking Nerf Herders.
The point here is that you may have a date system that is different to our world for various reasons (Your world has a 28 hour day cycle... or a 422 day annual cycle... or is like real world time, but the Norse Gods don't exist so they can't lend their names to the 7 days of the week). This shows a really decent amount of world building and attention to details that fans will appreciate... but how often do you name the day of a week in the fantasy genre (Harry Dresden and Potter might, because both are in genres that days of the week could matter on (the former is Fantasy Noir, and thus might comment on how it's an unusual Wednesday and the later is in a Fantasy Boarding School genre and will be in certain classes on certain days or off on the Weekends))?
A casual drop of an unusual day name in a common Euphamism that will translate to the readers (i.e. A talking camel declares Scigduleday his favorite day of the week, because it's Hump Da). This will immediately translate to the audience because the joke is referring to the famous Geico Commercial that features a talking Camel who is just so happy that it's Wednesday. The reader can infer that the date system is different in some way, because of the way the day is used in conjunction to our real world days. Scigduleday is clearly the middle of the work week. Thanking the Gods that it's Farramday will instantly line up with the TGIF of real life, and that Daantday Morning blues is clearly the beginning of the week.
It is not necessary for the reader to understand the dating system to get the joke that the days might be different but the sentiments about them remain. You can overbuild the world and show that there is constitantcy, either by making the jokes to show you thought about this, or if you have a spinoff, properly dating things (The Stardate system of Star Trek came in handy when it's consistent use in the TNG era was helpful for fans to know Chronology of the events that occured over two seperate television series and a movie franchise at it's peak in the 90s (TNG films, DS9, and Voyager all were in production at this time. The last episode of Voyage happens shortly before the last TNG movie (within a year of each other)).
Showing you created the system is what can be termed as Biblical information, which are documents and notes that one can use as rules for how the series operates. For example, J.K. Rowling first "outed" Dumbledoore during production of the Sixth movie as the original script had Dumbledoore refer to a young romance he had with a woman... because she had this information thought up for some time, she got the line removed from the script. This was sometime before she gave the more public outing. Similarly, the team of How I Met Your Mother, had to do several Biblical notes as the series progressed and they realized they needed to keep things consistent. They had had enough forwarning to shoot a scene in season 2 that would only be used in the season finale, which at the point in there production run, was not known to them (it was indeed used in the season 8 finale for the series).