The extended log file format is defined in the W3C Working
Draft WD- logfile-960323 specification by Phillip M. Hallam-Baker and Brian
Behlendorf. This document defines the Date and Time files to always be in GMT:
Date
<date> = 4<digit> "-" 2<digit> "-" 2<digit>
Dates are recorded in the format YYYY-MM-DD where YYYY, MM and
DD stand for the numeric year, month and day respectively. All dates
are specified in GMT. This format is chosen to assist collation using
sort.
Time
<time> = 2<digit> ":" 2<digit> [":" 2<digit> ["." *<digit>]
Times are recorded in the form HH:MM, HH:MM:SS or HH:MM:SS.S where HH
is the hour in 24 hour format, MM is minutes, and SS is seconds. All
times are specified in GMT.
This behavior is by design.