How to select holidays by date list?

Question

So I currently have my own made dashboard (CRUD). I work in React.js and Node.js (SQL).

export default function CreateDeveloper() {
    const url = "http://localhost:8080";
    const [name, setName] = useState("");
    const [slack_id, setSlackID] = useState(0);
    const [selected, setSelected] = useState("");
    const [absent, setAbsent] = useState("");


    const handleSubmit = (e) => {
        e.preventDefault();
        addDeveloper();
    }
    const addDeveloper = () => {
        Axios.post(`${url}/create`, {
          name: name,
          slack_id: slack_id,
          absent: absent,
          selected: selected
        }).then(() => {
            
        })
    }
    return (
        <form className='forms' onSubmit={handleSubmit}>
            <label>Slack ID:</label>
            <input type="text" onChange={(event) => { setSlackID(event.target.value) }} />

            <label>Absent:</label>
            <input type="number" min="0" max="1" onChange={(event) => { setAbsent(event.target.value) }} />

            <label>Name:</label>
            <input type="text" onChange={(event) => { setName(event.target.value) }} />

            <label>Selected:</label>
            <input type="number" min="0" max="0" onChange={(event) => { setSelected(event.target.value) }} />

            {/* Button Add Developer */}
            <button type="submit">add developer</button>
        </form>
    )
}

This is a segment of the code I have, its to create a new row. As you can see there is Absent. This is a boolean which is either 0 or 1. I'm trying to convert this into something different.

The question: Basically, Developers have free days and holidays, with this create method I want the Admin to be able to select multiple dates of whenever a developer is not around and store them into the database. However, I also need these dates to be linked with the Absent. So If a developer has an off day, The Date is linked with Absent, and Absent returns that he is absent.

Down the line there is more code which outputs a call to a slack bot and selects a certain developer, obviously people who are on holidays cannot be selected, I already have this created, but now I have to link the absent with certain dates of individual developer holidays.