[javascript] Convert JS date time to MySQL datetime

A simple solution is send a timestamp to MySQL and let it do the conversion. Javascript uses timestamps in milliseconds whereas MySQL expects them to be in seconds - so a division by 1000 is needed:

// Current date / time as a timestamp:
let jsTimestamp = Date.now();

// **OR** a specific date / time as a timestamp:
jsTimestamp = new Date("2020-11-17 16:34:59").getTime();

// Adding 30 minutes (to answer the second part of the question):
jsTimestamp += 30 * 1000;

// Example query converting Javascript timestamp into a MySQL date
let sql = 'SELECT FROM_UNIXTIME(' + jsTimestamp + ' / 1000) AS mysql_date_time';