presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/valueToSessionTimeZoneOffsetDiff
class DateTimeFunctions:    private static long valueToSessionTimeZoneOffsetDiff(long millisUtcSessionStart, DateTimeZone timeZone)
    {
        return timeZone.getOffset(0) - timeZone.getOffset(millisUtcSessionStart);
    }