Here's another interesting panel topic from Mile Hi Con
: the invisible assumptions that may be in our worldbuilding. Like the fish being unaware of the water in which it swims, we often don't even notice certain elements of our daily experience as being cultural
, and assume them as universals.
The title refers to the fact that most human cultures count by tens and multiples of tens -- most likely because we have ten fingers. However, it's not even a human universal -- there are cultures that count by twenties (found even in English in such formal and rather old-fashioned expressions as "Four score and seven years ago..."), and the Babylonians used twelves and even sixty as bases for numbering.
And from the Babylonians came our system of dividing the day into two sets of twelve hours, AM and PM, and subdividing the hour into sixty minutes and the minute into sixty seconds. Again, something that is easy to simply suppose as a universal, but isn't necessarily true even in historical human societies here on Earth (see traditional Chinese timekeeping
On the other hand, keeping with familiar conventions helps make writing more transparent and sensible to the reader. Much as you'll be writing your story in present-day English, even if your characters speak a language with no grammatical gender, aspect instead of tense, and prepositions formed from nominal phrases, presupposing the invisible translation of certain basic things like numbering system and time system for your fictional world may well make it more reader-friendly, especially if your POV characters are part of it, as opposed to Terrans visiting an alien world, where the differences accent its alienness.