Package to parse dates in Common Lisp?

This answer is very late but the local-time library is featureful and widely used. It is based on the article The long painful history of time.

It supports :

1. Time and date arithmetic
2. ISO 8601 timestring formatted output and parsing
3. Reader macros to embed timestrings directly in code
4. Timezone handling (will read unix tzfile format)
5. Conversion between universal and unix time epochs
6. Julian date calculation

Many implementations have a UNIX interface and, in same cases, this includes the strptime function.

You could try net-telent-date, which has PARSE-TIME which I think will do what you want.

It's now 2022, and net-telent-date is on github and is also deprecated. Better to find something else.

See the net-telent-date and simple-date-time libraries for Common Lisp. The former has a parse-time function you can use (see parse-time.lisp). Both are included in the QuickLisp library collection.