Here is a common question from this spring. It comes from the ISU answer line specialist, Richard Jauron and it originated from a county extension office in central Iowa.
The question is, "is this creeping Charlie/Ground Ivy (Glechoma hederacea)"? The answer is no, even though the leaves look like creeping Charlie. The pictures are of henbit (Lamium amplexicaule). Both are in the mint family (Lamiaceae) and both have square stems, but the henbit grows upright and does not spread like creeping Charlie.
The reason that we see so much henbit in the spring is that it is a winter annual. It germinates in the fall, often after herbicides have been applied. It then appears early in the spring. It is one of the reasons that I prefer late fall treatments with broadleaf herbicides, in October and even November over earlier treatments.
You can treat for it in the spring, but remember that your other landscape species are very susceptible to broadleaf weed controls at this time of year.