This is code that can be placed on Anki Cards to help

Calculate Exam Date

<div style="font-size:20px;color:#F2E48E;font-family:Times;
font-style:italic;letter-spacing:-2px;position:fixed;bottom:50px;
left:5px;opacity:.9;">
    <div class="editcloze">
        Ease: {{info-Factor:}}
    </div>
    <span id="countdown2"></span>
    <script>
        // ###### CUSTOMIZE DATE HERE ######
        var dateText= 'June 18 2022';
        var now = new Date().getTime();
        var targetDate= new Date(dateText).getTime();
        var dist = targetDate- now;
        var days = ((dist / (1000 * 60 * 60 * 24))/30).toFixed(1);
        document.getElementById('countdown2').innerHTML = days;
    </script>m (<span id="countdown"></span>
    <script>
        var now = new Date().getTime();
        var targetDate= new Date(dateText).getTime();
        var dist = targetDate- now;
        var days = Math.ceil(dist / (1000 * 60 * 60 * 24));
        document.getElementById('countdown').innerHTML = days;
    </script>d)
</div>

I'm currently studying in high school and I have a few subjects. I have different public exam dates for different subjects. However, I am using the same note type for different flashcards in different decks(each deck is a subject). so if I set the var dateText to a particular exam date, that would be the wrong date for other subjects. Is there anyway to solve this? Thanks!

Best way is just to use a different note type for each exam unfortunately.