sieve vacation - 2 questions

[Hajo Locke]

Hello,

still trying to move from procmail to sieve, but there are new problems.

Currently we use procmail for autoresponder and let user choose 
timerange, in which responder should work. May be you set up today your 
responder for 2 weeks in future where responder start and stop 
automatically without further manuell intervention.
In procmail this is done by simple scripting and comparison of 
timestamps. How to do this in sieve?

2nd questions concerns to used From-Address in responding mail.
Header of a sieve-responder shows a minimal From-Address:
From: <adress at example.com>
But our Users want to add a custom name which is displayed at recipient 
of responder:
From: John Doe <adress at example.com>
In procmail this is easy with formail, how to do this in sieve?
Both features we implemented because people asked about it. I should 
find a way to recreate this in sieve.

Thanks,
Hajo