IAM in Service Catalog
In general, use InCommon CA if the certificate is for website SSL, and UW CA if the certificate is for authenticating to a UW web service (e.g. student web service or person web service). For more information see CA comparison.
InCommon certificates have a maximum lifetime of two years starting 2018-03-01. This change affects all publicly trusted CAs. See CAB Ballot 193 for more information. The UWCA is not a publicly trusted CA and continues to issue three year certificates.