Year is an ambiguous unit as years are of varying length. Udunits defines a year as exactly 365 days. A time coordinate variable is identifiable from its units string, alone. The udunits routines utScan and utIsTime can be used to make this determination. The units attribute will be of character type.
Plural forms are also acceptable.
The direction of positive, whether up or down, cannot in all cases be inferred from the units. The direction of positive is useful for applications displaying the data. For this reason the new attribute positive is defined in this standard. The units attribute will be of character type with the string formatted as per the recommendations in the Unidata udunits package. A latitude coordinate variable is identifiable from its units string, alone.