Summary

The DAYS360 function calculates the number of days between two dates by treating every month as 30 days and every year as 360 days. That is not normal calendar math, but it is a standard rule in some finance and accounting work.

If you are working with loans, leases, or older financial models, you may need that fixed convention instead of actual days. That is where DAYS360 becomes useful.

Syntax

=DAYS360(start_date, end_date, [method])

DAYS360 takes a start date, an end date, and an optional method argument. The method changes how month-end dates are handled.

Most of the time, the default method is enough. If you are matching a specific accounting rule, the third argument matters more.

Arguments

• start_date - The starting date of the period.
• end_date - The ending date of the period.
• [method] - Optional. Use FALSE or omit it for the US method, and TRUE for the European method.

DAYS360 vs Regular Day Counts

DAYS360 is more specialized than regular date-difference functions. It is meant for standardized models, not for normal elapsed-time questions.

If you only want the real number of elapsed days, DAYS is usually the better choice. Use DAYS360 when the workbook needs to follow the 30/360 convention on purpose.

Using DAYS360

The main reason to use DAYS360 is consistency. In some models, February should not shorten the result and 31-day months should not make the result larger. The formula smooths those differences out.

The optional method argument is also important. The US and European versions can give different answers when dates fall at the end of a month, so it is worth checking which one your workbook is expected to follow.

• Use DAYS360 for accounting models that rely on a fixed 30/360 basis.
• Use the default method unless you specifically need the European rule.
• Do not use it when the real calendar day count is what matters.

That last point matters a lot. A formula can be mathematically correct and still be the wrong business choice if it is using the wrong day-count system.

Example 1 - Use the Default US Method

This is the standard starting point for DAYS360.

=DAYS360(B1, B2)

Excel uses the US method unless you tell it otherwise.

Example 2 - Use the European Method

If your model follows the European rule, pass TRUE as the third argument.

=DAYS360(B1, B2, TRUE)

This mainly matters around month-end dates such as the 31st.

Example 3 - Test the Result in a Logical Check

Because the result is numeric, it is easy to use in conditions.

=DAYS360(B1, B2) > 10

This returns TRUE or FALSE depending on the standardized interval.

Example 4 - Use the Result in an Accrual Formula

Many finance models multiply the day count by a daily amount or rate.

=DAYS360(B1, B2) * 10

This is a simple way to build a flat accrual calculation.

Conclusion Recap

DAYS360 is a specialized function, but it is very useful when a workbook follows a fixed accounting convention instead of the real calendar. The key is knowing when that convention is required.

• Core job: DAYS360 counts days using twelve 30-day months.
• Main use: It is common in finance, accounting, and older accrual models.
• Important option: The third argument switches between US and European handling.
• Key caution: It does not return actual calendar days.
• Practical use: The result works well in threshold tests and daily-rate formulas.