setTimeout() function is not executed properly - node.js

Question

I have to send an SMS 15 minutes before the appointment is there. I have written the code, but it is called at the time of execution itself. Is there any other method or how do I solve this?
"RP.remindePatient" is the function that has to be called 15 minutes before the appointment time.
sendApptConf(s) {
var number = Phone;
var msg = urlencode("Hello " );
var smsData = 'username=' + username + '&hash=' + hash + '&sender=' + sender + '&numbers=' + number + '&message=' + msg;
var options = {
host: 'api.textlocal.in',
path: '/send?' + smsData
};
var callback;
console.log(options);
callback = function (response) {
var str = '';
// Another chunk of data has been recieved, so append it to `str`
response.on('data', function (chunk) {
console.log("new Data received")
str += chunk;
console.log(str);
});
// The whole response has been received, so we just print it out here.
response.on('end', function () {
console.log(str);
});
}
http.request(options, callback).end();
// Send SMS using Textlocal DONE
const convertTime = consultDate + ' ' + consultTime;
var d = new Date(convertTime);
var ms = d.getTime();
var milliLess15 = ms - (15 * 60 * 1000);
console.log(milliLess15);
setTimeout(function () {
console.log("I should be called after some delay")
RP.remindePatient(userPhone, patientName, drName, consultMode, consultDate, consultTime, transId, email, paymentDetails);
}, milliLess15);

Answer 1

I think there is a small issue in your logic. As you would already know, setTimeout(function () {}, milliseconds) will fork the function() after milliseconds you have specified.
Now let's focus on the below snippet of code:
const convertTime = consultDate + ' ' + consultTime;
var d = new Date(convertTime);
var ms = d.getTime();
var milliLess15 = ms - (15 * 60 * 1000);
Let's say your appointment is at 12:00 pm today (in millisec let's say 1492776423) and current execution time is 10:00 am (in millisec 1485576423). By your logic, you are calling the function() after: var milliLess15 = ms - (15 * 60 * 1000) which is 1492776423 - (15 * 60 * 1000) = 1491876423. Note here that, you don't want to call function() after 1491876423 millisec. Rather you want to call it after millisec equivalent of 12:00 - 10:00 - 00:15. So your logic should look something like:
const convertTime = consultDate + ' ' + consultTime;
var d = new Date(convertTime);
var ms = d.getTime();
var currentTime = new Date();
var currentTimeMilli = currentTime.getTime();
var milliLess15 = ms - (15 * 60 * 1000) - currentTimeMilli;
Rest of the code will remain the same. Hope this answer helps you!

Answer 2

Don't call the variable after timeout. Just put in:
setTimeout(function () {
console.log("I should be called after some delay")
RP.remindePatient(userPhone, patientName, drName, consultMode, consultDate, consultTime, transId, email, paymentDetails);
}, 900000);