Build time stamp in google sheets

Job ID: 30812555

Budget: ₹600 – ₹1,500 INR

https://docs.google.com/spreadsheets/d/11AURj2PQJ5ois-1zc71NxN7k157zYg3UBx4hQbymmI0/edit?usp=sharing
This is the link to the google sheet for which I want the time stamp.
This is the checklist of a team member (Ashok) of my office.
In sheet 1, 'Row I' consists of the tasks and 'Row H' is the time by which those tasks needs to be completed. From Row J onwards are the dates.
As soon as Ashok completes his task he will write 'Y' against that task in the cell of the current date & if task is not completed then he will write 'N'. The time at which he writes Y or N, I want that time to reflect in sheet 2. Earlier I tried using NOW command but its not working.
Related categories: Excel Google Sheets