Wireshark-dev: Re: [Wireshark-dev] frame_data.abs_ts and pcap timestamp reference

From: Guy Harris <guy@xxxxxxxxxxxx>
Date: Wed, 9 Dec 2009 09:47:28 -0800

On Dec 9, 2009, at 6:32 AM, RUOFF LARS wrote:

Is frame_data.abs_ts /* Absolute timestamp */ given in UTC or local
time?

UTC.

Can someone give me a hint on where to search for the code that does the
conversion before display (if any)?

abs_time_to_str(), etc. in epan/to_str.c.

Do pcap files store timestamps in UTC or local time?

UTC. See, for example, the pcap-savefile man page in libpcap 1.0.0 and later, or

	http://wiki.wireshark.org/Development/LibpcapFileFormat

If UTC, do they store the time zone?

In theory, yes. In practice, no. There is a time zone offset field in the file header, but no application (tcpdump, *thereal/*shark, etc.) has ever set it to anything other than 0, as far as I know (I know that libpcap, which is what most applications use to write the files, sets it to 0).