Creating a Global Variable (number) and then making a rule to set this variable to "current time" in "seconds" will result in the variable becoming the current unix time, which is the elapsed time since January 1st, 1970. It will display this number as the number of seconds elapsed since 1970 or the amount of milliseconds elapsed since 1970 your choice in RM. I use this feature in some GV calculations for filter changes. Here are the screen shots to illustrate it:
The test rule I made
The result
Current Unix time: https://time.is/Unix
Don't know if this feature will help you accomplish what you want, but it is there if you need it.
