JSFiddle - React, Tailwind, and code Playground

JavaScript

var decalage        = +1
    var decalage_minute = 50
    
    var d = new Date( ); //date
    		
    //convert date timestamp
    function decalage_f( date, decalage, decalage_minute )
    {
        var data = new Date( date.getTime( ) + ( decalage * 60 * 60 * 1e3) + ( decalage_minute * 60 * 1e3 ));
        return data;
    }
    
    var data = decalage_f ( d, decalage , decalage_minute );

    alert( data.getHours( )  + ":" + data.getMinutes( ) );