Many people hold that one should not make kiddush on Shabbos between the hours of 6 and 7. (Sources: Shulchan Aruch Harav and Taamei Haminhagim, (who, in turn, bring a Maharil, a Magen Avraham, and a Rashi in Shabbos)).
The thing that confuses me is that all the people I know who do this, count the hours by the clock rather than the halachic time. This includes following the clock with time zones, and daylight savings. So, regardless of whether Shabbos starts at 4:30 or 8:00, they will avoid kiddush between 6 and 7.
My question is, does this make any sense at all? Is there any source for following the clock? Furthermore, even if we do follow the clock, can there be any reason to follow daylight savings time?