Hi David,
Those 2 methods are legacy, that is how the old time zone adjustments were made which did not automatically adjust for Daylight savings. I kept the old methods for compatibility with Mono since the new TimeZoneInfo class is not yet fully supported under Mono.
Best way to do it now is to use code like:
TimeZoneInfo timeZone = SiteUtils.GetUserTimeZone();
DateTime localDate = DateTime.Parse(dpBeginDate.Text);
DateTime utcDate = TimeZoneInfo.ConvertTimeToUtc(localDate, timeZone);
DateTime localDate2 = TimeZoneInfo.ConvertTimeFromUtc(utcDate, timeZone);
Best,
Joe