I don’t think benching with a kos is not m’akev in any situation on any day, it’s just preferable.
ubi: I don’t think standard time would matter, since the custom is based on when goyim see you pouring wine ( the concern of blood libel). I talked to some people who do still keep this, and they said when the clocks change between Daylight Savings and back, it makes no difference; ie. they don’t have to shift it by an hour. Maybe not everyone figures it this way. I’m not sure, who, other than Chabad, keeps this minhag.