There is a preUpgrade folder that is created before each update in the QIE Home Directory. Usually located at C:\ProgramData\QIE
The date on that folder will show the date of the update.
Also in the QIE folder, you can find the realease-notes.txt which has a log of the dates of when each release was made available.
With the next release of 2.0.44 or thereafter the release notes can be viewed from within the System Administration -> System Configuration under the QIE Update Status.