Moustached Darter (Sympetrum vulgatum) or Common Darter (Sympetrum striolatum) - because of yellow stripe on backside of the legs and the general markings on abdomen and thorax. Only saw it like this.
The amount of yellow on the legs indicate a Common, which is also the one flying earliest of the two. But to id the two with confidence other details, like the moustache of the eye or shape of the vulva scale, has to be seen.
A very early individual, but maybe the many hours with sun we've had during April and May has provoked and early setoff among insects in general.