code: @Nullable
    public static String getAsStringW3C (@Nullable final LocalDateTime aDateTime)
    {
      if (aDateTime == null)
        return null;
      return getAsStringW3C (aDateTime.atOffset (ZoneOffset.UTC));
    }
docs: create a W3C Date Time representation of a date.
  
  @param aDateTime
  Date to print. May not be <code>null</code>.
  @return the W3C Date Time represented by the given Date.