DATEVALUE
Returns the internal date number for text in quotes.
The internal date number is returned as a number. The number is determined by the date system that is used by Office to calculate dates.
If the text string also includes a time value, DATEVALUE only returns the integer part of the conversion.
This function is part of the Open Document Format for Office Applications (OpenDocument) standard Version 1.2. (ISO/IEC 26300:2-2015)
Syntax
DATEVALUE("Text")
Text is a valid date expression and must be entered with quotation marks.
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 recognised 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 Tools - Options - Office Calc - Formula, button Details... in section "Detailed Calculation Settings", Conversion from text to number list box.
Example
=DATEVALUE("1954-07-20") yields 19925.