When was MyBitcoin created? MyBitcoin used to be an online Bitcoin shared eWallet. It was the go-to place for easily handling bitcoins. The site eventually shut down with a major loss of coins, widely suspected to be perpetrated by the service operator.

Its time of closing down is well known (July 2011) but I could not find a reference for when it was opened.

(Potentially relevant reading: What is the story behind MyBitcoin?, How much Bitcoin was lost in the Jul. 2011 MyBitcoin site shutdown incident?)
The mybitcoin.com domain existed no earlier than 2010-04-25, according to the domain name registration record (whois).

According to the mybitcoin.com history at archive.org, the domain first appears to have useful content sometime in early February 2011.

In case the above archive.org url doesn't work (seems to have a problem for me), copy and paste it from here:

https://web.archive.org/web/20110315000000*/http://www.mybitcoin.com