week navigation bugged on year shift

This still happens: If you click "previous week" from simplereservation/2/2010 -- you are taken to simplereservation/52/2009.

Also, the days are off by one: For example it says "Monday, 17.01.2010" when it really should be "Monday, 18.01.2010"

Workaround:
Edit the simplereservation.modules and look for:

  $config["week"] = $week;

  $config["prev_week"] = $week - 1;
  $config["prev_week_year"] = $year;
  $config["prev_4week"] = $week - 4;
  $config["prev_4week_year"] = $year;
  if (date("z", $date) < 7)  { //if ($week == 1)
    $config["prev_week"] = 52;
    $config["prev_week_year"] = $year-1;
    $config["prev_4week"] = 48;
    $config["prev_4week_year"] = $year-1;

and change it to:

  $config["week"] = $week;

  $config["prev_week"] = $week - 1;
  $config["prev_week_year"] = $year;
  $config["prev_4week"] = $week - 4;
  $config["prev_4week_year"] = $year;
  if (date("z", $date) < 7)  { //if ($week == 1)
  $config["prev_week"] = $week - 1;
  $config["prev_week_year"] = $year;
  $config["prev_4week"] = $week - 4;
  $config["prev_4week_year"] = $year;

This will flawlessy get you a week or a month back in time. When you hit the year-switch (so week 1 jan 2010) and press back the module will not understand it, so this is still a bug.
For me this workaround solves this big problem but create another small one.

Let me know if this is sufficient to solve you problem.

if you instead change it to:

$config["week"] = $week;

$config["prev_week"] = $week - 1;
$config["prev_week_year"] = $year;
$config["prev_4week"] = $week - 4;
$config["prev_4week_year"] = $year;
if ($week <= 4) {
$config["prev_week"] = $week - 1;
$config["prev_week_year"] = $year;
$config["prev_4week"] = 52 - (4 - $week);
$config["prev_4week_year"] = $year - 1;
}
if ($week == 1) {
$config["prev_week"] = 52;
$config["prev_week_year"] = $year - 1;
}

the year change will work correctly

Changed week view from date.module's "calendar weeks" to ISO weeks to fix this and other bugs.

Committed to the -dev version, give it up to 12h to be repackaged.