# Add-in Functions

The following describes and lists some of the available add-in functions.

You will also find a description of the LibreOffice Calc add-in interface in the Help. In addition, important functions and their parameters are described in the Help for the Shared LibraryLibreOffice Calc add-in DLL.

## Add-ins supplied

LibreOffice contains examples for the add-in interface of LibreOffice Calc.

\<bookmark_value\>DAYSINMONTH function\</bookmark_value\>\<bookmark_value\>number of days;in a specific month of a year\</bookmark_value\>## DAYSINMONTH

Calculates the number of days of the month in which the date entered occurs.

DAYSINMONTH(Date)

Date: Any date in the respective month of the desired year. The Date parameter must be a valid date according to the locale settings of LibreOffice.

DAYSINMONTH(A1) returns 29 days if A1 contains 2/17/68, a valid date for February 1968.

\<bookmark_value\>DAYSINYEAR function\</bookmark_value\>\<bookmark_value\>number of days; in a specific year\</bookmark_value\>## DAYSINYEAR

Calculates the number of days of the year in which the date entered occurs.

DAYSINYEAR(Date)

Date: Any date in the respective year. The Date parameter must be a valid date according to the locale settings of LibreOffice.

DAYSINYEAR(A1) returns 366 days if A1 contains 2/29/68, a valid date for the year 1968.

\<bookmark_value\>ISLEAPYEAR function\</bookmark_value\>\<bookmark_value\>leap year determination\</bookmark_value\>## ISLEAPYEAR

Determines whether a year is a leap year. If yes, the function will return the value 1 (TRUE); if not, it will return 0 (FALSE).

ISLEAPYEAR(Date)

Date specifies whether a given date falls within a leap year. The Date parameter must be a valid date.

ISLEAPYEAR(A1) returns 1, if A1 contains 2/29/68, the valid date 29th of February 1968 in your locale setting.

You may also use =ISLEAPYEAR(DATE(1968;2;29)) or =ISLEAPYEAR("1968-02-29") giving the date string in the ISO 8601 notation.

Never use ISLEAPYEAR(2/29/68), because this would first evaluate 2 divided by 29 devided by 68, and then calculate the ISLEAPYEAR function from this small number as a serial date number.

\<bookmark_value\>MONTHS function\</bookmark_value\>\<bookmark_value\>number of months between two dates\</bookmark_value\>## MONTHS

Calculates the difference in months between two dates.

MONTHS(Start date, End date, Type)

Start date: First date

End date: Second date

Type: Calculates the type of difference. Possible values include 0 (interval) and 1 (in calendar months).

\<bookmark_value\>ROT13 function\</bookmark_value\>\<bookmark_value\>encrypting text\</bookmark_value\>## ROT13

Encrypts a character string by moving the characters 13 positions in the alphabet. After the letter Z, the alphabet begins again (Rotation). By applying the encryption function again to the resulting code, you can decrypt the text.

ROT13(Text)

Text: Enter the character string to be encrypted. ROT13(ROT13(Text)) decrypts the code.

\<bookmark_value\>WEEKS function\</bookmark_value\>\<bookmark_value\>number of weeks;between two dates\</bookmark_value\>## WEEKS

Calculates the difference in weeks between two dates.

WEEKS(Start date, End date, Type)

Start date: First date

End date: Second date

Type: Calculates the type of difference. The possible values are 0 (interval) and 1 (in numbers of weeks).

\<bookmark_value\>WEEKSINYEAR function\</bookmark_value\>\<bookmark_value\>number of weeks;in a specific year\</bookmark_value\>## WEEKSINYEAR

Calculates the number of weeks of the year in which the date entered occurs. The number of weeks is defined as follows: a week that spans two years is added to the year in which most days of that week occur.

WEEKSINYEAR(Date)

Date: Any date in the respective year. The Date parameter must be a valid date according to the locale settings of LibreOffice.

WEEKSINYEAR(A1) returns 53 if A1 contains 2/17/70, a valid date for the year 1970.

\<bookmark_value\>YEARS function\</bookmark_value\>\<bookmark_value\>number of years between two dates\</bookmark_value\>## YEARS

Calculates the difference in years between two dates.

YEARS(Start date, End date, Type)

Start date: First date

End date: Second date

Type: Calculates the type of difference. Possible values are 0 (interval) and 1 (in calendar years).

## Add-ins through LibreOffice API

Add-ins can also be implemented through the LibreOffice API.