Date-time must be a POSIXct, POSIXlt, Date, chron, yearmon, yearqtr, zoo, zooreg, timeDate, xts, its, ti, jul, timeSeries, and fts objects.
a date-time object
A logical. TRUE if DST is in force, FALSE if not, NA if unknown.
A date-time's daylight savings flag can not be set because it depends on the date-time's year, month, day, and hour values.
x <- ymd("2012-03-26") dst(x)#>  FALSE