If you want to calculate how much time is left until a certain expiry date, you can use the DATEDIF function. This function returns the difference between two dates in terms of days, months, or years.

Easy way to calculate time difference in Excel using simple logic. A simple formula to calculate difference between two dates & times in Excel.

Percentages aren't always easy to calculate, but one of the best tools in Excel's toolbox is calculating percentages for you. Here's how to do it.

The article How to calculate conditional subtotals in an Excel revenue sheet uses simple expressions, a function, and a conditional format to display a daily balance in a revenue sheet.