The timestamps on comments in journals using S1 display in the timezone of the InsaneJournal servers, which is US Pacific Standard Time (-800 GMT) or, when applicable, US Pacific Daylight Time (-700 GMT). The timestamps on comments in journals using S2 display using the GMT timezone. The times on comments are automatically assigned when they are posted; there is no way to set or edit the time on a comment.
When viewing comments anywhere on InsaneJournal, you will need to take into account this time difference in order to work out the local time at which the comment was posted.