Documentation/Calc Functions/MONTHS

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Function name:

MONTHS

Category:

Date and Time

Summary:

Calculates the number of months between two dates.

Syntax:

MONTHS(StartDate; EndDate; Type)

Returns:

Returns an integer value which is the difference between the two given dates in months, depending on the calculation mode selected through the Type argument.

Arguments:

StartDate is the date (in quotation marks) or a date-time serial number, or a reference to the cell containing one of those types, which is either the start date or the end date of the period for which the calculation is to be carried out.

EndDate is the date (in quotation marks) or a date-time serial number, or a reference to the cell containing one of those types, which is either the end date or the start date of the period for which the calculation is to be carried out.

Type is an integer value, either 0 or 1. If Type is 0, then MONTHS returns the number of whole months between StartDate and EndDate (day of the month to day of the month). If Type is 1, MONTHS identifies the month that each of StartDate and EndDate lie in, and then returns the difference between those months. See the #Additional details: and #Examples: sections below for more detail.

  • If either StartDate or EndDate is not a valid date expression, then MONTHS reports a #VALUE! error.
  • If StartDate is earlier than EndDate, the result is a positive number; if StartDate is later than EndDate, the result is a negative number.
  • MONTHS ignores any time components of StartDate and EndDate.
  • If Type is non-numeric, then MONTHS reports a #VALUE! error.
  • If Type is a non-integer value, then MONTHS truncates it to an integer.
  • If (after truncation) Type is not equal to either 0 or 1, then MONTHS reports an invalid argument error (Err:502).

Additional details:

Details specific to MONTHS function

If Type is set to 1, the equation for MONTHS is

MONTHS = MONTH(EndDate) - MONTH(StartDate) + 12 * (YEAR(EndDate) - YEAR(StartDate)).

If Type is set to 0, the value calculated above is adjusted as follows:

  • If (StartDate is earlier than EndDate) and (DAY(StartDate) > DAY(EndDate)) then subtract 1
  • If (StartDate is later then EndDate) and (DAY(StartDate) < DAY(EndDate)) then add 1.

MONTHS is not part of the ODF 1.2 international standard and should not be regarded as portable.

General information about Calc's Date and Time functions

Note pin.svg

For convenience the information in this subsection is repeated on all pages that describe functions in the Date and Time category.


  • Internal to Calc, a date/time value is handled as a real number and this is sometimes referred to by the term date-time serial number. For example, 2021-02-08 12:00:00 corresponds to the date-time serial number 44235.5. The integer part of a date-time serial number (before the decimal point) is the number of days since a defined start date. The fractional part of a date-time serial number (after the decimal point) is the time of day expressed as a fraction of a day. For example, 0.25 is equivalent to 06:00:00 and 0.75 is equivalent to 18:00:00.
  • Calc uses 1899-12-30 as the default start date (day 0) but you can go to Tools > Options > LibreOffice Calc > Calculate to select alternative start dates; however, unless you have specific requirements for compatibility with legacy spreadsheet applications, we recommend that you do not change this setting. If you copy and paste cells containing date values between different spreadsheets, check that both documents are set to use the same start date to avoid unexpected changes to the dates displayed.
  • Negative date-time serial numbers correspond to dates earlier than Calc's start date. Calc calculates all dates back to 15th October 1582 using the Gregorian calendar. The day before this is 4th October 1582, and Calc uses the Julian calendar for earlier dates.
  • A date-time serial number is the same as any other number, except that we usually choose to display it formatted as a date/time. You can enter a number in a cell and then change the cell’s formatting to display the value as a date/time. You can also enter a date/time in a cell and then change the cell’s formatting to display the date-time serial number.
  • For clarity, the descriptions of the Calc functions within these wiki pages use the standard ISO 8601 format for date and time because this should be independent of your selected locale settings. The default date format on your computer may be different. When entering dates as part of formulas, slashes or dashes used as date separators may be interpreted as arithmetic operators. Therefore, dates entered in this format are not recognized as dates and result in erroneous calculations. To keep dates from being interpreted as parts of formulas either use the DATE function or place the date in quotation marks and use the ISO 8601 notation. Avoid using locale dependent date formats which may produce errors if the document is loaded under different locale settings.
  • Time zone information is not used by Calc’s Date & Time functions.
  • If you only wish to enter two digits of the year (for example 21 instead of 2021), Calc needs to know whether you mean 2021 or 1921. Go to Tools > Options > LibreOffice > General to view or adjust the range of years which Calc will use to interpret two-digit year values.
  • Calc contains logic to decide how to treat text when encountered as an operand in an arithmetic operation or as an argument to a function that expects a number instead. In this context, unambiguous conversion is possible for ISO 8601 dates and times in their extended formats with separators. For example, the simple formula =1 + "2021-02-08" will usually give the result 2021-02-09 (when formatted as a date). However, this logic may be affected by the settings on the Detailed Calculation Settings dialog, accessed by selecting Tools > Options > LibreOffice Calc > Formula and pressing the Details button in the Detailed Calculation Settings area. If a #VALUE! error occurs, it may be because the Generate #VALUE! error option is selected, in which case you should experiment with one of the other self-explanatory options in the Conversion from text to number drop-down.

Examples:

Formula Description Returns
=MONTHS("2020-04-01"; "2021-06-15"; 0) Here the function returns 14, the number of months between the two dates. 14
=MONTHS("2020-04-01"; "2021-06-15"; 1) Here the function again returns 14, the number of months between the two dates. In this case the value of the Type argument makes no difference to the result. 14
=MONTHS("2020-10-31"; "2020-11-30"; 0) Here the function returns 0 when Type is set to 0. In this case, the period is not considered to be a full month, despite the two dates being the last days of their months. 0
=MONTHS("2020-10-31"; "2020-11-30"; 1) Here the function returns 1, when Type is set to 1. 1
=MONTHS(F1; 44166; F2) where cell F1 contains the date 2020-11-30 and cell F2 contains the value 0. 44166 is the date-time serial number for the date 2020-12-01. Here the function returns 0 when Type is set to 0. 0
=MONTHS(F1; 44166; F3) where cell F1 contains the date 2020-11-30 and cell F3 contains the value 1. 44166 is the date-time serial number for the date 2020-12-01. Here the function returns 1 when Type is set to 1. Although the two dates are on consecutive days, they are in different months. 1
=MONTHS("2020-05-08"; "2010-01-01"; 0) Here the function returns -124. The StartDate is later than the EndDate. -124

Related LibreOffice functions:

DAYS

YEARS

ODF standard:

None.

Equivalent Excel functions:

None.