More than a couple of our vendors have been frustrated by my insistence that they properly support daylight saving time. Both switch overs have their own set of unique potential problems but if a vendor has an API as part of their product and we're going to build automation on top of it, this twice a year undefined behavior generator isn't acceptable. It surprises me how many companies seem to have an severe allergy to using UTC or even including TZ data with their time/date data.

Most libraries like Java time choose the earlier timezone (summer) by default, but allow an override. If the date picker parses text you can usually force it to one of the two times pass explicitly setting the offset.