createDateTime is not a valid date format

While transferring an application from a ColdFusion 9 server to a ColdFusion 10 server, it produced the following error:
createDateTime is not a valid date format

I was able to trace the error to the following line:
parseDateTime(myDate, 'yyyymmdd')

(Of note is that the troublesome line does not actually call createDateTime. Maybe it does under the hood?)

The myDate variable was the result of a createDate call, and looked like this:
{ts '1985-10-26 00:00:00'}

I have no idea why ‘yyyymmdd’ was specified as the expected format, nor do I know why CF9 was more forgiving about it than CF10. If you run into this error, the format parameter is definitely something to check.

As an aside, the Adobe documentation is terrible as usual:

It lists 2 parameters, date/time string and pop-conversion, but gives no examples of the latter. And of course there is a 3rd parameter, the date format. This is the documentation for CF11–as far as I can tell there is no pop-conversion parameter in CF10 or earlier–but the page does not clearly indicate which version it covers, nor does it provide a link to the same content for earlier versions.