Combine text format date and time to date_time format

Recently my friend do ask me about combining date and time which written in two different column. The purpose was to find different between those 2 date/time i.e time taken to complete a process.

Sample of original data as follow;
Date & time in two different cell
Purpose : To find time difference between process 1 & 2


The solution;First

i. Convert date and time format to text, use TEXT function if the date format not converted to text, date will be define as number
such as 40,118 for 1st Nov 2009 instead of 1/11/09

Second
i. Combine both date & time text using CONCATENATE function,
tips : follow standard date & time format setting i.e dd/mm/yr_hh:mm am/pm