# Calendar Logic 2: Day Number Formula

### Here's a simple formula to consider with day numbers of a month, considering the 7 possible columns:

### y = 7x ± b

### y = day number, x = row number & b = column number

Ever notice that on monthly calendars, all of the Sundays, Mondays, Tuesdays, etc. have numbers that are **7 integers**
apart? That's because there are **7 days in a week!** If today is the 1st day of the month & a Wednesday, then the next Wednesday will be
the 8th day of the month! In fact, you can check the *linear functions* for each month column in the images below:

#### The character in the picture is Mr. Quentin Clockwise.

Note: The top row is numbered **zero(0)** because it simplifies the math considering the 1st day of the month. Also, did you notice that I
put the plus-or-minus symbol (±) in the formula at the top of the Web page? That's because *negative numbers* are very important in this formula! A
column of a monthly calendar can be numbered with a negative number, like you can see in 2 of these 3 calendars! __Adding negative numbers turns addition into
subtraction!__

The variable *b* in the formula is always equal to **zero(0)** on the column that comes before the 1st day of the month. If the 1st day of
a month is a Sunday, then this variable (*b*) will always be a *positive number!* The maximum possible number that *b* can be
**+7** & the minimum is **-5**.

#### Sometimes, the bottom row will only have blank day spaces! In this row, *x* = 5.

Conclusively, since the months of the year have at most **31 days**, the variable *y* will always leave a blank day space if it's
equal to **32 or more!** It also leaves blank day spaces where it's less than **1.** I decided to only use monthly calendars with exactly **31 days**
to keep things simple; however, if the month is **February**, then the variable *y* will leave blank day spaces when it's
greater than **28.** (Or **29** during leap years!) If the month is **April, June, September or November**, then the variable *y* will leave blank day spaces when it's
greater than **30.**

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© Derek Cumberbatch