Syntax
set aDateTime = aString.parseDateTimeExpression(aFormat)
Semantics

parseDateTimeExpression() initializes a DateTime object from a string using the given format expression. The format expression is a string with placeholders for date/time variables (see Date and Time Formatting).

The operation expects that aString conforms to the given format aFormat. If the string does not match with the given format, the xUML Runtime will raise an exception and not parse the string.
If conformity to the format is not guaranteed, you can use the match() Operation on aString to check before using parseDateTimeExpression.

SubstitutablesaString Can be any variable or object attribute having the type String.  
aFormat Can be any variable or object attribute having the type String. The formatting rules can be found in Date and Time Formatting.
Error CodesFind the related error codes on System Errors.
FUDSM/9 Parsing of "..." failed, it does not match format expression "...".
Examples
set aDateTime = aString.parseDateTimeExpression("%d.%m.%Y %H:%M:%S");

Example File (Builder project E2E Action Language/BaseTypes):

<your example path>\E2E Action Language\BaseTypes\uml\formatExpressions.xml