Within this context TimeTicks are UNIX timestamps.
Unix time, or POSIX time, is a system for describing points in time: it is the number of seconds elapsed since midnight UTC of January 1, 1970, not counting leap seconds. It is widely used not only on Unix-like operating systems but also in many other computing systems.

Syntax
set aTimeTick = aDateTime.convertDateTimeToTimeTicks();
Semantics convertDateTimeToTimeTicks() converts a DateTime object to a Unix timestamp.
SubstitutablesaDateTimeCan be any variable or object attribute having the type DateTime. 
aTimeTickCan be any variable or object attribute having the type Integer.
Examples
set aTimeTick = aDateTime.convertDateTimeToTimeTicks();