function date_week

The calendar week number for a date.

PHP week functions return the ISO week, not the calendar week.

Parameters

string $date: A date string in the format Y-m-d.

Return value

int: The calendar week number.

File

core/includes/date.inc, line 1027

Date API functions.

Code

function date_week($date) {
  $date = substr($date, 0, 10);
  $parts = explode('-', $date);
  $first_day = config_get('system.date', 'first_day');

  $date = new BackdropDateTime($date . ' 12:00:00', 'UTC');

  // If we are using ISO weeks, this is easy.
  if ($first_day == 1) {
    return intval($date->format('W'));
  }

  $year_date = new BackdropDateTime($parts[0] . '-01-01 12:00:00', 'UTC');
  $week = intval($date->format('W'));
  $year_week = intval(date_format($year_date, 'W'));
  $date_year = intval($date->format('o'));

  // Remove the leap week if it's present.
  if ($date_year > intval($parts[0])) {
    $last_date = clone($date);
    date_modify($last_date, '-7 days');
    $week = date_format($last_date, 'W') + 1;
  }
  elseif ($date_year < intval($parts[0])) {
    $week = 0;
  }

  if ($year_week != 1) {
    $week++;
  }

  // Convert to ISO-8601 day number, to match weeks calculated above.
  $iso_first_day = 1 + ($first_day + 6) % 7;

  // If it's before the starting day, it's the previous week.
  if (intval($date->format('N')) < $iso_first_day) {
    $week--;
  }

  // If the year starts before, it's an extra week at the beginning.
  if (intval(date_format($year_date, 'N')) < $iso_first_day) {
    $week++;
  }

  return $week;
}