Koen, we did a bit more research on this and SiteCatalyst also allows to manually override the server timestamp via s.timestamp variable.
From the SiteCatalyst documentation here are some requirements:
1.) The ReportSuite must be configured to receive custom time stamps, after this is enabled ALL requests to that Report Suite must contain the s.timestamp or they will be rejected.
2.) Timestamps must be in either UNIX or ISO-8601 format. The following restrictions apply to ISO-8601:
- Both date and time must be provided, separate by a "T" [ex: 2012-04-20T12:49:31-0700]
- The date must be a calendar date with full precision (year, month, and day). Week dates and ordinal dates are not supported.
- The date can be in standard or extended format (YYYY-MM-DD or YYYYMMDD) but they must include hour and minute (seconds are optional) (HH:MM, HH:MM:SS, HHMM, or HHMMSS). Fractional minutes and seconds can be passed in, but the fractional parts are ignored.
- An optional timezone can be specified in standard or extended format (+/-HH, +/-HH:MM, +/-HHMMM, or Z)