I just stumbled across an undocumented script function called UC4_BUILD_DATE that returns the build date of the AE.
Script
:SET &UC4_Build_Date# = UC4_BUILD_DATE()
:PRINT "UC4 build date : &UC4_Build_Date#"
Output
U00020408 UC4 build date : 2018-07-11
This is the same date one sees at the top of the AE server log.
U00003400 Server 'AE_1#WP' version '12.0.5+hf.2.build.1839' (changelist '1531143975') started.
U00003327 Build Date: '2018-07-11', '06:17:25'