today i am buy new Airpods Gen 2. but i cant register purchase date .

Hello najeeb212,

It seems like you will need to contact Apple Support to update/correct the purchase date issue. Update your proof of purchase - Apple Support

Below I have pasted how to get various things Apple Support will ask you for

"Get the agreement number or proof of coverage

1. Go to mysupport.apple.com.
2. Sign in with your Apple ID.
3. Choose your device. 
4. Click View Proof of Coverage. If you don't see your proof of coverage, make sure that you set up your Apple ID with two-factor authentication."

Find information about your warranty or AppleCare plan - Apple Support

"Looking for the serial number?

You can find the serial number of your AirPods in the same place as the model number—follow the steps at the beginning of this article. If necessary, you can learn other ways to find the serial number."

Identify your AirPods - Apple Support

From the same article: "Find the model number

You can use the model number of your AirPods to find out which generation of AirPods you have. Here's how to find the model number. 

Look in Settings

1. Go to Settings > Bluetooth.*
2. Find your AirPods in the list (for example, "John's AirPods"). 
3. Tap the Info button  next to your AirPods, and you'll see the model number.

* If your device doesn't have iOS 14 or iPadOS 14 or later and your AirPods are connected to your device, you can find the model number by going to Settings > General > About. Then scroll down until you see the name of your AirPods, and then tap the name."

Keep your receipt after you buy an Apple device - Apple Support This has what needs to show on the Sales Receipt.

I hope this helps,

• Scott (he, him)