Wireshark · Wireshark-bugs: [Wireshark-bugs] [Bug 11349] Potentially wrong dissection of Time Zone (DST not taken into account i

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Pascal Quantin changed bug 11349

What	Removed	Added
CC		pascal.quantin@gmail.com

Comment # 1 on bug 11349 from Pascal Quantin

Hi,

this is not my understanding of the spec.

The encoding of the timezone byte is:
"The Time Zone indicates the difference, expressed in quarters of an hour,
between the local time and GMT. In the first of the two semi octets, the first
bit (bit 3 of the seventh octet of the TP Service Centre Time Stamp field)
represents the algebraic sign of this difference (0: positive, 1: negative)."

So when the byte contains the value 0b01000000, it corresponds to 4*15mn = 1
hour, which is your delta between Winter or Summer.

So basically what the spec says is that the Time Zone field should contain the
DST also, and not only the time zone. It does not imply that bit 3 of the Time
Zone byte is an indication of DST presence.

For example with a DST of +2 hours and a Winter time zone of 0b00000000, the
Summer Time Zone byte would have been: 0b10000000.

Do you agree?

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