If you want to highlight dates that occur in the next N days with conditional formatting, you can do so with a formula that uses the TODAY function with AND. This is a great way to visually flag things like expiration...

To determine invoice status (i.e. paid, open, overdue), you can use a nested IF formula and the TODAY function.
In the example shown, the formula in G5 is:
=IF(F5=0,"Paid",IF(TODAY()<C5,"Open...

You can set up dynamic calendar grid on an Excel worksheet with a series of formulas, as explained in this article. In the example shown, the formula in B6 is:
=start-CHOOSE(WEEKDAY(start),0,1,2,3,4,5,6)
where "start...

To calculate the days remaining from one date to another, you can use a simple formula that subtracts the earlier date from the later date.
In the example shown, the formula in D5 is:
=C5-B5
How this formula works...

If you need to display the current date in a worksheet, you can use the TODAY function. This date will update whenever the worksheet is recalculated or opened.
Here's how the formula works:
The TODAY function takes no...

Note: Excel has several built-in data validation rules for dates. This page explains how to create a your own validation rule based on a custom formula in case you want or need more control and flexibility.
To allow a...

To calculate the number of days before a certain date, you can use subtraction and the TODAY function. In the example, D5 contains this formula:
=B4-TODAY()
How this formula works
In Excel, dates are simply serial...

To create a dynamic date list, you can use a formula that increments a start date to create and display additional dates. In the example shown, the formula in B5 is:
=start+ROWS($B$5:B5)-1-offset
where "start" is the...

T calculate the number of days between two dates you can simply subtract the older date from the newer date. The result will be an integer that represent the days between dates. In the example shown, the formula in D6...

To sum sales in the last 30 days by an id (like name, initials, region, etc.) you can use the SUMIFS function together with the TODAY function. In the example shown, the formula in G5, copied down, is:
=SUMIFS($D$5:$D...

Note: Excel has several built-in data validation rules for dates. This page explains how to create a your own validation rule based on a custom formula if you need more control or flexibility.
To allow a user to enter...

To highlight dates that are "past due" you can use a conditional formatting and a basic formula to check whether each date is less than today. In the example shown, conditional formatting has been applied to the range...

Note: Excel has several built-in data validation rules for dates. This page explains how to create a your own validation rule based on a custom formula when you want more control and flexibility.
To allow only a date...

If you need to calculate a person's age from their birth date, you can do so with the YEARFRAC, INT, and TODAY functions. In the generic version of the formula above, birthdate is the person's birthday with year, and...

To calculate the number of workdays remaining in a month, you can use the NETWORKDAYS function. NETWORKDAYS automatically excludes weekends, and it can optionally exclude a custom list of holidays as well.
In the...