EDATE
The result is a date which is a number of months away from the start date. Only months are considered; days are not used for calculation.
This function is part of the Open Document Format for Office Applications (OpenDocument) standard Version 1.2. (ISO/IEC 26300:2-2015)
EDATE(開始日; 月)
開始日 は、日付です。
月 は、開始日の前 (負の数) またはあと (正の数) の月数です。
When entering dates as part of formulas, slashes or dashes used as date separators are 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 use the DATE function, for example, DATE(1954;7;20), or place the date in quotation marks and use the ISO 8601 notation, for example, "1954-07-20". Avoid using locale dependent date formats such as "07/20/54", the calculation may produce errors if the document is loaded under different locale settings.
Unambiguous conversion is possible for ISO 8601 dates and times in their extended formats with separators. If a #VALUE! error occurs, then unselect Generate #VALUE! error in LibreOffice - PreferencesTools - Options - LibreOffice Calc - Formula, button Details... in section "Detailed Calculation Settings", Conversion from text to number list box.
2001年3月31日より1ヶ月前の日付を求めます。
=EOMONTH(DATE(2001;9;14);6) は、シリアル値 37346 を返します。日付形式にすると 2002-03-31 です。