How can employee calculate their notice period?

The notice period is calculated based on employee's company’s policy. Company policy specifies the notice period as the number of days from the date of submission of employee's resignation. Once the employee submits the resignation and the company's management approves the last working day, the employee's notice period starts.

For example: 

Your company’s policy for the notice period is 30 days. You submitted your resignation on 1st September. Then your Last Working Day(LWD) is 30 days from the date of your team member’s resignation submission, i.e., 30th September.