PHP:按日期查询数据库,但我想手动更改日期

I am programming a prayer book using a DB that contains readings for each day of the church calendar (a digital lectionary). The page code is fairly simple PHP that uses the current date to determine which day of the church calendar it is. Here is where I get the date:

$dateinput = date('Y-m-d');
$dateTime = strtotime(date('Y-m-d'));
$dateDt = date('Y-m-d', $dateTime);
$year = date('Y',$dateTime)."<br>";

Then I find, based on Christmas, Easter, etc. what season of the church calendar it is, what week of that season, and what day of the week.

And then I select the row that matches that season, week, and day:

$result = mysqli_query($link,"SELECT * FROM prayer WHERE Year='$lectionaryYear' AND SuperSeason='$superSeason' AND Week='$week' AND Day='$dayOfWeek'");

It works well, but I would like to be able to click an arrow to look at yesterday's readings or tomorrows readings. Is this possible? I know PHP is server side, and what I'm imagining would be client-side, so maybe this just isn't an option.

The final result is here.

You can use the $_GET variable and pass the dates to the url via your back and forth buttons.

Your href would look like this

<a href="http://www.example.com/?date=<?php echo date('Y-m-d', strtotime('-1 DAY')); ?>">Back</a>

And then use the date for your query.

$_GET['date']