Almost certainly solar time.

We had software choke on a birth date once. For some reason these were sent in milliseconds, and that particular instance, midnight July 1st, 1937 didn't exist for this particular locale. At that time, the time was changed to a different meridian, and the clock was moved forward a few seconds.

In the 1940s, the nazis set all of occupied Europe to Berlin time, and it stuck. Before that time, Europe had a large number of time zones.