Maxima Function
elapsed_real_time ()
Returns the number of seconds (including fractions of a second) since Maxima was most recently started or restarted. The return value is a floating-point number.
Example:
(%i1) elapsed_real_time (); (%o1) 2.559324 (%i2) expand ((a + b)^500)$ (%i3) elapsed_real_time (); (%o3) 7.552087