Timer

PHP: Start and stop a timer PHP - Stack Overflow

MySQL: Recording the time elapsed after the sql query was executed.

SELECT @timer := CURRENT_TIMESTAMP();
SELECT SLEEP(2); /* sleep 2 seconds for testing purpose */
SELECT 'custom message' AS 'action', CURRENT_TIMESTAMP() AS 'end time', @timer AS 'start time', TIMEDIFF(CURRENT_TIMESTAMP(), @timer) AS 'time elapsed';

Linux or Cygwin commands on Win

START=$(date +%s)
sleep 2s
END=$(date +%s)
DIFF=$(( $END - $START ))
echo "Elapsed time $DIFF seconds"

Python: performance - Measure time elapsed in Python? - Stack Overflow