Hi
I think you could use something like this.
The OP in that case was trying to use the local time, as converted from timestamp, to name files. The solution should be the same: you also want to convert the timestamp into your local time, if I unerstood your post corretly. Just substitute filename for your newts, play with the time format, and you should be good to go.
This will not change @timestamp itself (and apparently there are reasons why you shouldn't), but you will get a variable with the local time that you can use.
Hope this helps