All terms in the Immigration law are stated in days, not months.
However, Argentine law (Civil Code, section 25) states that terms of months or years end on the same day the respective month has, regardless of the number of days the months or years have. Thus, a term beginning on the 15th of a month, will end on the 15th of the respective month.
If the month in which the term starts has more days than the month in which in term ends, and if the term runs from one of the days when the first of these months exceeds the second, the term will end on the last day of second month (Civil Code, section 26). Both are free translations, if in doubt, check the original in Spanish (http://www.infoleg.gov.ar/infolegIn...9/109481/texactley340_preliminar_tituloII.htm
On the other hand, you don't have to do a Colonia Renewal every 90 days. You may renew your tourist visa -only once- staying in Argentina. Thus, you could stay up to 180 days without leaving the country.
If you have any further doubts, you may contact us at www.fandinoabogados.com
or by email at [email protected]