Timestamped Signature for Netbeans Module

I'm currently trying to create a sgned NBM in order to publish it in the Plugin Portal. 

Unfortunately I'm always getting the following warning:


Code:
The signer certificate will expire within six months.
No -tsa or -tsacert is provided and this jar is not timestamped. Without a timestamp, users may not be able to validate this jar after the signer certificate's expiration date (2016-03-27) or after any future revocation date.




As far as I know my plugin will stop working once the expiration date is reached. 

I know how to extend the livetime of my certificate but this will only postpone the expiration and is IMO no real solution.

Now I'm wondering how to create a timestamped signature in order to keep the plugin working once the expiration date is reached.

Unfortunately I did not find a way to pass the -tsa option to the signing process.

I'm using Maven and I'm following the steps as described in http://wiki.netbeans.org/DevFaqSignNbm

I'm using JDK 1.8

How can I create a timestamped signature?