Spoiler in brief for those who don't know the ending yet:
At the end, Phileas Fogg alongside with his companions realize that they have arrived back to London a day earlier than expected due fact the party did travel eastward.
Each time they crossed the known time-zone(s), they adjusted their (pocket-)clocks an hour backwards (sans Passepartout. depending on the adaptation / source), which each time roughly gave them an extra hour to win the wager (the details regarding to "won" amount of time differs a bit in each adaptation of the novel).
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That famous ending should be a quite simple one.
But how about something a bit more modern with essentially same result, only the whole process lasts over an year (using a real, up-to-date-calendar will help during "perceiving"-phase:
- You're being paid exactly every-fourth-full-week on Friday (E.G. during 2015 first on February 27th, then on March 27th, then on April 24th, and so worth).
+ On those paydays, you also start paying your apartment-rent upfront (E.G. on the payday of February 2015, you're paying the rent of March 2015, and so forth).
-> By continuing paying the rent like this for roughly 12-months (less even, to be precise), you will end up into a situation in which you're paying the upcoming rent over a month before hand (E.G. on February 2016, you're already paying the rent of April 2016).
For the sake of information-sharing alongside providing yet even more material to help with "perceiving"-phase, here is a link to an example "payday-model" from real-life:
Labour Market Subsidy in Finland
As the title of this question hints, I am indeed looking a term / name for "mathematical-phenomenon" alongside a simple as possible formula for simple people.