Age calculator app width grid and flex

Can anyone tell me if this logic is right, I have some doubts 🤔. JS:

    const day = document.getElementById('day')
    const month = document.getElementById('month')
    const year = document.getElementById('year')
    const amont_of_days = new Date(parseInt(year.value), parseInt(month.value), 0).getDate()
    let total_years = parseInt(current_year - year.value)
    let total_months = 12 - parseInt(month.value)
    let total_days = parseInt(day.value - current_day)
    if(current_month < month.value){
        total_years -= 1
    }
    if(current_day > day.value){
        total_months += 1
    }
    if(total_days < -1){
        total_days = total_days * -1
    }