TIMEVALUE /text/scalc/01/func_timevalue.xhp TIMEVALUE function

TIMEVALUE

TIMEVALUE returns the internal time number from a text enclosed by quotes and which may show a possible time entry format. The internal number indicated as a decimal is the result of the date system used under $[officename] to calculate date entries. If the text string also includes a year, month, or day, TIMEVALUE only returns the fractional part of the conversion. TIMEVALUE("Text") Text is a valid time expression and must be entered in quotation marks. =TIMEVALUE("4PM") returns 0.67. When formatting in time format HH:MM:SS, you then get 16:00:00. =TIMEVALUE("24:00") returns 0. If you use the HH:MM:SS time format, the value is 00:00:00.
TIMEVALUE wiki page.