iWork Numbers How To Calculate - In Once Cell Function - The Elapsed Time In Hours Between Two Date/Times?
Assuming I have understood what you wish to accomplish correctly, here is one way of doing it in the same cell if you are willing to enter the dates and the times separately:



And here is the text version of the formula shown above

=(DATEDIF(DATE(2020,5,29),DATE(2020,5,30),"D")+TIMEVALUE("02:30")−TIMEVALUE("20:30"))×24


Unfortunately, this can not be done by entering the date &amp; time together for each point in time (or without entering them more than once). It appears that there is no date &amp; time function in Numbers that calculates the difference between two date &amp; time values in hours directly or one that fully converts a date &amp; time value in text or otherwise to a proper date &amp; time value that Numbers can process.