Undefined parameter [time]

I’m tried to use the special variable time within the expression of a behavioral current source but for some reason ngspice does not like this.
The manual claims that these variable exists.
The same behavior applies to hertz and temper.
Could someone give me an example of how to use these?

There is an example in chapter 5.1.1 of the ngspice manual.
Use the xhtml manual at Ngspice User's ManualVersion 39 plus(ngspice development version) for copying, as the pdf manual adds a lot of unwanted spaces in wrong places.