## Explanation

In Excel, the concept of "weekday" or "day of week" is based on the idea that each day of of the week has a specific number. With default settings, the WEEKDAY function treats Sunday as the first day of the week (1), and Saturday as the last day (7). When given a valid date, the WEEKDAY function will return a number between 1 and 7.

To find the next day of week, this formula first rolls the date forward by 7 days, then steps back to the correct date by subtracting the result of a calculation that uses the WEEKDAY function. In the example shown the formulas in row 6 are as follows:

```
=B6+7-WEEKDAY(B6+7-7) // C6, get next Saturday
=B6+7-WEEKDAY(B6+7-2) // D6, get next Monday
```

In the first formula (C6), the number 7 (at the end) represents Saturday. In the second formula (D6), the number is 2, for Monday.

In D6, the formula is solved like this:

```
=B6+7-WEEKDAY(B6+7-2)
=42027-WEEKDAY(42025)
=42027-4
=42023
=1/9/2015
```

*Note: when the given date is already the desired day of week, the original date will be returned.*

### Next day of week from today

To get the next day of week from the current date, you can use the TODAY function, like so:

```
=TODAY()+7-WEEKDAY(TODAY()+7-dow)
```