How do you use the now function

[kestral]

I have seen a few examples and read the documentation but have been unable to get the now function to return a value. I'm using ver 3.0.0 of Zabbix and have tried the following

now
now()
now(0)
last(vfs.file.time[{$RHH.CTREE_BACKUP_FOLDER}\BACKUP.DAT]).now
...