Week-Based Calendar

The calendar that we are normally using is unnecessary difficult: you cannot really tell which day of the week a given date falls on. What if, instead, we used weeks an weekdays? That would make it immensely easier to interpret the dates.

Fortunately, there is already an international standard for that: ISO week numbers. The ISO week starts on Monday (as it does in the most countries in the world).

The number of weeks in any given year can be calculated as:

$$\mathrm{YEAR\_END}\left(y\right)=(y+\lfloor \frac{y}{4}\rfloor -\lfloor \frac{y}{100}\rfloor +\lfloor \frac{y}{400}\rfloor )mod7$$ $$\mathrm{WEEKS}\left(y\right)=\{\begin{array}{ll}53& \text{if}\mathrm{YEAR\_END}\left(y\right)=4\text{or}\mathrm{YEAR\_END}(y-1)=3\\ 52& \text{otherwise}\end{array}$$