Record Date- If you own the shares on the designated date, which is also known as the record date, you are deemed an eligible shareholder in the company's records.
When a firm announces corporate activities such as the entitlement of right shares, bonus shares, stock splits, dividends, and so on, qualified shareholders are entitled to receive advantages or adjustments.
Ex-Date: The ex-day is the date on which a stock begins trading ex-benefit, that is, without the benefit of corporate action. After two trading days from the day of purchase in India, shares are delivered to your Demat account. Until the ex-dividend date, a stock is considered to trade with the benefits of the corporate action, or cum-benefit (i.e. cum-rights, cum-dividend, etc.). After that, it trades without the benefit, or ex-benefit.
Let's look at an example to help you understand:

Assume that a corporate action's record date falls on a Wednesday.

1) This stock's ex-date will be Tuesday, one day before the record date.

2) You'll be eligible for corporate action if you buy the stock earlier than Monday or earlier than Monday.

3) The stock is said to be cum - corporate action up until Monday, which means it gains from the corporate action.

4) The stock is said to trade ex-corporate action starting Tuesday.

5) You will not receive the advantage of corporate action if you purchase the stock after Monday.
Except in the following circumstances, you will always receive the shares you purchased after two trading days:

1. Settlement holiday -If the record date falls on a settlement holiday, the shares will be delivered on the next working settlement day. Assume that Wednesday was a settlement holiday in the previous case. If you buy the shares on Monday, you'll get them on Thursday (after the record date) and won't be able to participate in the corporate action.

To ensure that the shares are available in your Demat account on the record date, you must purchase the stock at least one trading day prior to Monday.
2. Short delivery - Short delivery occurs when the seller on the other side of your trade fails to deliver the shares. The exchange will hold an auction in this case and deliver the shares to your Demat account by T+3 day. So, if you buy shares on Monday but don't get them until Thursday or later owing to delayed delivery, you won't be eligible for the corporate action because you didn't have the shares in your account on the record date