Interface DateOrBuilder (2.7.4)

Day of a month. Must be from 1 to 31 and valid for the year and month, or 0 to specify a year by itself or a year and month where the day isn't significant.

int32 day = 3;

Month of a year. Must be from 1 to 12, or 0 to specify a year without a month and day.

int32 month = 2;

Year of the date. Must be from 1 to 9999, or 0 to specify a date without a year.

int32 year = 1;