YYYYMMDDToDate(num)
YYYYMMDDToDate32(num)
YYYYMMDDhhmmssToDateTime(num, [timezone])
YYYYMMDDhhmmssToDateTime64(num, [resolution], [timezone]) -- no fraction arg, it's implicitly extracted from floating point or decimal num.

-- returns the same data type as dt:
changeYear(dt, new_value)
changeMonth(dt, new_value)
changeDay(dt, new_value)

-- if argument is Date - returns DateTime, if Date32, returns DateTime64:
changeHour(dt, new_value)
changeMinute(dt, new_value)
changeSecond(dt, new_value)