cdm/src/main/java/ucar/nc2/units/DateUnit.java
public String makeStandardDateString(double value) {
    Date date = makeDate(value);
    if (date == null) return null;
    DateFormatter formatter = new DateFormatter();
    return formatter.toDateTimeStringISO(date);
  }
public String makeStandardDateString(double value) {
    Date date = makeDate(value);
    if (date == null) return null;
    DateFormatter formatter = new DateFormatter();
    return formatter.toDateTimeStringISO(date);
  }
Make a standard GMT string representation from this unit and given value.

@param value of time in these units.
@return String or null if not time unit.