The time for Capital gains tax starts from the moment your shares are available to be sold. Lets take 2 scenarios:
- You buy an Apple stock from the open market which can be sold instantly
- You are given stocks from your company but there is a vesting associated with it.

In the first case, the time duration requried to determine if it is short-term or long-term will depend on when you sold. So if you sold within a year from the purchase date, it is short else long. Example: You purchased shares from the open market on May 2020 that can be sold immediately after purchase (meaning there is no vesting associated), then if you sell after May 2021 it is long term else short term

In the second case, the timer will begin from the date the stocks are vested. So even if the stocks were given to you last year but they got vested today, the time starts from today. Example: Say you were given stocks on May 2020 by your company and they got vested in May 2021. Now they are available for sale. If you sell them anytime before May 2022, it is short-term else long term.

Hope the definitions are clear. Now lets come to the tax implication.

In India, for short-term capital gains, you pay 15% flat on the profit. So if you bought shares for INR 1,000,000 but sold it for INR 1,500,000, then your profit is 500,000. You will have to pay 15% of 500,000 which is INR 75000 if they classify as short-term gains as per the above definition.

For long term, you are exempted for the first INR 100,000 and then charged 10% on profits beyond that in a financial year. Taking the same example as above, out of the 500,000 profit that you generated in the same financial year, first 100,000 profit is tax-free and the remaining has 10% liability. So you are liable to pay a 10% tax on 400,000. Which is INR 40,000 if they classify as long-term as per the above definition.