excel - Converting a string to a date in a cell -

i have 100.000 rows of data in excel. of fields dates, fields in excel text. need these fields in number format including both dates , time (e.g. 21.10.2011 13:10:50). formatting cells doesn't work because doesn't change datatype. can pick out date , time formulas not them in same cell.

so looking formula calculate number representation of date (the 1 see if format date number).

have tried =datevalue() function?

to include time value, add functions together:

=datevalue(a1)+timevalue(a1)