From time to time, you need to count days of week between two dates or in some date range (see How to count days of week in the range of dates). Excel proposes different formulas to work with data. It is easy to create the formula you need for this task:

From time to time, you need to count days of week in some date range or between two dates (see How to count days of week between two dates). Excel proposes different formulas to work with data. It is easy to create the formula you need for this task:

When calculating the difference between two dates, you may want to exclude weekends and holidays. You can see how to calculate the number of Working Days between two dates for the usual, standard working week where weekends are Saturdays and Sundays.

If you use formulas in Excel, you often can see messages such as #VALUE! or #DIV/0!. Most of the time, this means you need to check the source of the error and fix it, but sometimes a formula error simply means that the data used by the formula is not yet available.

By default, when you work in Excel, it automatically identifies all issues, such as incorrect data in the cell, problems with formulas, etc. So, you see green triangles (by default) shown in the top left corner of these cells.

Sometimes, especially when you work with a lot of data, you need to transform it. If you need to convert some range of data by dividing or multiplying it, it can be done in Excel in two clicks:

Use COUNTIF if you need to sum values for a particular person or another criterion.

Use SUMIF if you need to sum values for a particular person or another criterion.

You can usually view formulas in an Excel cell when the cell is selected, but you can protect a spreadsheet by hiding the formulas in some cells.

Often you'll want to insert a series of dates into a worksheet. The most efficient way to enter a series of dates doesn't require any formulas - just use Excel's AutoFill feature.