Development versions of capinfos have the -S option, which should make 
this easier:
   −S  Display the start and end times as seconds since January 1, 1970.
       Handy for synchronizing dumps using editcap −t.
Salman Malik wrote:
Thank you sake ! Isn't there any other way?I mean, if I could direclty 
put in an arbitray date, without predating/postdating timestamps . I 
don't want to do the nasty calculations time and again...
------------------------------------------------------------------------
From: sake@xxxxxxxxxx
Date: Sun, 7 Mar 2010 16:30:14 +0100
To: wireshark-users@xxxxxxxxxxxxx
Subject: Re: [Wireshark-users] PCAP date change ?
You can use editcap (shipped with Wireshark):
  -t <time adjustment>   adjust the timestamp of each packet;
                         <time adjustment> is in relative seconds (e.g. 
-0.5).
(from editcap -h)
Cheers,
Sake
On 7 mrt 2010, at 16:08, Salman Malik wrote:
    hello
    how can I change pcap files's date of capture ? I want to merge two
    files, recorded after 2 month of another...
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