Time() is not defined in Sugarcube

Hi all!

I'm trying to store the time it takes for each user to go through a passage and thought about using the time() function in Sugarcube.
I declared a variable and I'm setting it like this afterwards:

<<set $a1 = time()>>

but I get the message that 'time' is not defined.
I also tried using Date.now() inside a <<script>> tag but no luck there either Any clues?