Need to know the date of purchase from serial number.

If your product was registered, had a warranty, and you bought it new

or as an official Apple refurb product from them directly, it may appear

in a web page such as here (you likely need to be logged into see)

https://getsupport.apple.com/GetproductgroupList.action

You may also look into Support where one may look if trying to get service.

There, you'd have to know the serial number & put it in a blank.

https://getsupport.apple.com/ProductSelector.action

If neither of these do it, you may have to see if the online Store can

show you a list of products by date of purchase. This may only

tell you if they may be covered, and the info they show has changed

since I last looked up stuff; bought long enough ago for no warranty.

https://selfsolve.apple.com/agreementWarrantyDynamic.do

And items from several years ago in my list, do not show dates.

Good luck & happy computing! 🙂

If you bought the item through a store you could walk in and ask

a manager if they could help you find their record; however it you

bought the item with a debit or credit card, ask the sponsoring bank.

Usually there is more than just one receipt, and a proof-of-purchase

can sometimes be kept with the packaging the product was in new.

Since these ASC discussions are a user-to-user forum, and seldom

has any direct input from Apple directly (except a few specialists

and some moderation) information such as you ask about is not

directly available to us; and some of us don't reply, others search

the Apple site pages to see if there is anything offered.

Sorry if none of the links or phone numbers to Apple, authorized

resellers, or service providers also available from the Contact Us

in the web page lower border, have been helpful either.

Good luck & happy computing! 🙂

You may be able to generally identify the build year series of the device

by using a 'serial number lookup' service, or Apple support database;

that may at least show you about when it was built and correctly place

the product manufacture date within known specific model series.

Identify by serial number can be helpful in several ways, but not by

itself a means to personally re-trace the time of retail purchase if

the unit has no active AppleCare or other dated plan in effect.

See the links generated by this google search:

https://www.google.com/?gws_rd=ssl#q=identify+ipad

Indirect and not exact approximate purchase date info can be found

in this way, and since you said one of the Apple site pages told you

the unit was out-of-warranty, by use of serial number there. You may

be able to find out more about the unit itself, but not the purchase date.

If you had purchased an extended AppleCare plan, that may have let

the unit be more readily seen in the database, due to a record of when

the plan (in future, if active) would expire. Care plans add a known time

after a purchase date.

identify your products by serial or model number: (if in database)

https://www.powerbookmedic.com/identify-mac-serial.php

Was there a specific purpose requiring the purchase receipt that can't

be achieved by other methods, given you can closely identify the iPad

to a fair degree of accuracy with the serial number...?

While there may be a way to find the info you seek, most methods that

may be helpful are not open to the public or may involve internal records.

Thought to look again, and reply as I searched online. The topic has

come up in several guises in user forums, concerning several products.

You could try to call Apple main sales number for sales support and

ask them if you could speak to a product specialist, about this issue.

Someone could tell you some thing as simple as when the warranty

expired by date, which would tell you when it was sold at retail.

Good luck & happy computing! 🙂