Skip to content

DAYS360 Function

The DAYS360 function in Excel calculates the number of days between two dates based on a 360-day year, which assumes each month has 30 days. This function is frequently used in financial and accounting systems to simplify date calculations.

Syntax

DAYS360(start_date, end_date, [method])
  • start_date: The starting date of the period. It must be in a valid Excel date format or a reference to a cell containing such a date.
  • end_date: The ending date of the period. It must also be in a valid Excel date format or a reference to a cell containing such a date.
  • method (optional): A logical value (TRUE or FALSE) specifying the method to use:
    • FALSE or omitted: Uses the US (NASD) method, where the first day of a month and the last day of a month are handled differently.
    • TRUE: Uses the European method, where dates are treated consistently, and all months are assumed to have 30 days.

Returns

The DAYS360 function returns an integer that represents the number of days between the two dates based on the chosen 360-day year model.

Key Features

  • Simplified Date Diff: Approximates the duration between two dates using a uniform 360-day year.
  • Choice of Method: Supports both US and European calculation methods for compatibility with different financial systems.
  • Handles Edge Cases: Specific rules account for irregularities like end-of-month dates.

Example Usage

Example 1: Default (US NASD Method)

Suppose you have two dates in cells A1 (2023-01-01) and A2 (2023-12-31).

=DAYS360(A1, A2)

This formula returns 360, assuming the US method.

Example 2: European Method

If you want to use the European method for these same dates:

=DAYS360(A1, A2, TRUE)

This formula also returns 360, but it treats the dates using European rules.

Example 3: End-of-Month Edge Case

For US-specific handling of end dates like January 30 and February 28:

=DAYS360(DATE(2023,1,30), DATE(2023,2,28))

This formula returns 30 if using the default US method.

Notes

  • Both start_date and end_date must be valid dates. Invalid dates will result in a #VALUE! error.
  • Typically used in financial and accounting applications that require uniform month lengths (12 months x 30 days = 360 days/year).
  • The function simplifies interest calculations, payment schedules, and other financial planning tasks.

Use Cases

  • Loan and Lease Agreements: Compute daily interest and payment periods based on a standardized 30-day month.
  • Financial Forecasting: Provides more predictable calculations for accounts payable/receivable timelines.
  • Accounting Systems: Aligns with financial standards that use a 360-day year to harmonize date differences.

The DAYS360 function is a specialized tool designed for consistent, predictable date-based calculations in financial models and accounting software.