Common Excel Date Functions - Documentation

This Microsoft article can help explain more. For example, understanding how the Function Dialog (fx) Box works as shown below can help:

This web page serves as a tutorial guide covering some common key functions you should know.

The purpose of the TODAY() function is to return todays current date.

This function takes in no arguments (inputs) and it's syntax is as follows: =DATE()

This function will update automatically when the worksheet changes or opens. Typically by default Excel workbooks are set to update Automatically. This can be confimred by going to:
Formulas (tab) -> Calculation (group) -> Caluclation Options

The 'F9' key is a shortcut key used to manually recalculate the worksheet and update the value if it doesn't update. The user can also go to:
Formulas (tab) -> Calculation (group) -> Calculate Now (F9) to force a manual update.

Since the output is a date, you can format the result in a different date number format if needed (e.g. YY-MM-DD, MM-YYYY, etc).

NOTE: To insert a fixed date and time that won't update, use these keyboard shortcuts:
Current date: Press Ctrl + ;
Current time: Press Ctrl + Shift + :

To see the date one week from today, use this formula:
= TODAY() + 7 // one week in the future

The WEEKNUM() function takes in the week number for a given date argument. This argument must have a valid Excel date.

= WEEKNUM(09-21-1994)

The Excel WEEKDAY function returns a number from 1 to 7 for a given date, showing which day of the week it is.

By default, Sunday is 1 and Saturday is 7, but that can always be changed. It’s useful in formulas when you need to check or work with days of the week.

=WEEKDAY("05/05/2025") // => Output: 2

If you want Monday to be 1 and Sunday to be 7 instead, you can add a second argument:

=WEEKDAY("05/05/2025", 2) // => Output: 1

This will return 1, since now Monday is treated as the first day of the week.

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The WORKDAY function returns a date that is a certain number of working days before or after a starting date.

It is typed as '=WORKDAY' and it is formatted as:

=WORKDAY(start_date, days, [holidays])

The WORKDAY function helps calculate dates by skipping weekends and, if provided, holidays. It’s most often used for scheduling project due dates/deadlines and planning deliveries.

Suppose a task takes 5 working days and starts on Monday, May 5, 2025. Using the formula
="5-May-2024"+5 // returns "10-May-2024"
outputs a day on a Saturday. Since this result is a weekend and we want to count only weekdays, instead we'll use:
=WORKDAY(TODAY(), 5) // returns "12-May-2024"
which gives the date five working days from today, excluding weekends, which will land on the 12th.

NOTE: The WORKDAY.INTL function lets you set which days are weekends and how many there are.

The most common example of WORKDAY is looking at a WBS project schedule:

As shown, we'll use the WORKDAY function to look at the dates the project tasks are due.

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The DATEDIF function returns the number of days, months, OR years between two dates.

=DATEDIF(start_date,end_date,unit)

NOTE: "If you want to find the number of days between two dates, simply subtract the later date from the earlier date. This works because dates are stored as numbers in Excel." - Source from Microsoft

The NETWORKDAYS function returns the number of working days between two dates, excluding weekends & holidays.

We can use NETWORKDAYS to track time worked or benefits and optionally skip a list of holidays.

=NETWORKDAYS(
start_date,
end_date,
[holidays]
)

Please look at the following example:

Project Info

In the above example, we can do:
=NETWORKDAYS(B2,B3,B4:B7)