Iterative addition of a column from a file

Question

I have an input file like below:

input.txt

number       date               duration     revenuecode   
------       -----------        --------     ------------    
890011,      20160307104312,     120,         CCF9000000VV    
890011,      20160307104312,     120,         CCF9000000NN    
890011,      20160307104312,     120,         CCF9000000CC

Some information about the columns:

• date column – uses the YYYYMMDDhhmmss format
• duration column – uses seconds

Using the content of the file I have to create a new one which has to update the date column:

• Date value in 1st row: Date [@1st row]
• Date Value in 2nd row: Date [@1st row] + 120 sec. ["Date revised value" @ row2]
• Date Value in 3rd row: ["Date revised value" @ row2] + 120 sec. ["Date revised value" @ row3]

Is there any function in shell script that does such iterative addition for a specific column (from a file)?