Per dobedobedoh's review of MDL-81282, commented here:

lib/db/install.xml: <FIELD NAME="timeend" TYPE="int" LENGTH="10" NOTNULL="true" DEFAULT="2147483647" SEQUENCE="false"/>

lib/enrollib.php:define('ENROL_MAX_TIMESTAMP', 2147483647);

I suspect that both of these are values are used because they were the 32-bit max value and that we can move towards the 64-bit max now.

Second case would be a straight replacement, not sure how we'd use the constant in the XML file though. To investigate