calendar date getting back -1 day, what is wrong, alternate solution? - php

Question

I'm trying to go back one day in the calendar – What am I doing wrong?
My approach:
$weekdays = array('Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun');
///////
function getDates($year) {
$dates = array();
date("L", mktime(0, 0, 0, 7, 7, $year)) ? $days = 366 : $days = 365;
///
for($i = 1; $i <= $days; $i++) {
// get Unix timestamp for a date
$month = date('F', mktime(0, 0, 0, 1, $i, $year));
$wk = date('W', mktime(0, 0, 0, 1, $i, $year));
$wkDay = date('D', mktime(0, 0, 0, 1, $i, $year));
$day = date('d', mktime(0, 0, 0, 1, $i, $year));
///
$dates[$month][$wk][$wkDay] = $day;
}
return $dates;
}
//////
$year = 2020; // from this Year
$dates = getDates($year);
$countW = 1; // for counting weeks
// Output code
echo '<h2><span>Calendar '.$year.'</span></h2>';
foreach($dates as $month => $weeks) {
echo '<div>';
echo '<table>';
echo '<caption>'.$year.' '.$month.'</caption>';
echo '<tr>';
echo '<th>W</th>';
echo '<th>'.implode('</th><th>', $weekdays).'</th>';
echo '</tr>';
echo '<tr>';
foreach ($weeks as $week => $days){
echo '<tr><td>'.$countW++.'</td>';
foreach ($weekdays as $day) {
echo '<td>';
/* I'm overwhelmed here! */
echo isset($days[$day]) ? $days[$day] : date('d', strtotime('-1 day')); // outputted is 5
echo '</td>';
}
echo '</tr>';
}
echo '</tr>';
echo '</table>';
}
I tried the following codes:
date('d', strtotime('-1 day')) // outputted: 5 (today is 6)
$jd = gregoriantojd(01,06,2020); echo jddayofweek($jd,2); // outputted: Mon (today is Tue)
With this code I get the day from the current day before.
It is expected the day before the specified day
what is happening
is expected

Answer 1

With this code I get the day from the current day before. It is expected the day before the specified day
The day that is "specified" here date('d', strtotime('-1 day')) is the current day.
Generally speaking, a (American) monthly calendar will leave a blank space if the day is not in the month. For example:
That would be a super simple fix to the problem. If not, you'll need to adjust your thinking (and the code!). In the case of the first week of January, the dates for Mon and Tues are -2 and -1 from the first day of January. Similarly, in the last week they are -2 and -1 from the first day of February (or +1, +2 from the last day of January).