Develop Reference

convert time to 00d 00h 00m

I want it to show the time in this style: 00d 00h but I don't know how it could show just 24 hours in a day and not total hours
what shows: 10d 170h
what I want to: 10d 08h
Math.floor((Date.now() - member.user.createdAt) / 86400000)}d ${Math.floor((Date.now() - member.user.createdAt) / 60 * 60 * 24 * 1000)}h

You can mod the hour total by 24 ,meaning every 24 hours it will 'rotate' back to 0
console.log(Math.floor((Date.now()) / 86400000)+"d"+ Math.floor((Date.now()) / ( 60 * 60 * 24 * 1000)%24)+"h");

How to calculate the latitude of the subsolar point (ie. solar declination) using javascript?

I am trying to calculate the point on Earth where the sun is directly overhead using javascript. My function for longitude works great, but I am having trouble with the latitude.
I understand that what I am looking for is called the Solar Declination, and an approximate formula for that is (source):
δ=23.45 * sin[(360/365)(284+N)]
where N is the day in the year, where January 1 is 1, Feb 1 is 32, etc.
This is the function I am using now:
function getSolarDeclination(){
return -23.44 * Math.sin( (360 / 365.25) * getDayOfYear() )
}
function getDayOfYear(){
var now = new Date();
var start = new Date(now.getFullYear(), 0, 0);
var diff = now - start;
var oneDay = 1000 * 60 * 60 * 24;
var dayOfYear = Math.floor(diff / oneDay);
return dayOfYear + 284
}
However, this doesn't seem to be giving me the right number. For today, June 3, 2020, I am getting 17.607657911890687, whereas at least according to this site it should be ~22.465. This is several hundred miles off!
What am I doing wrong? Is this approximate formula just too "approximate"?

Looks like the formula you're using expects values in degrees, but Math.sin uses radians. If you convert it, it gives roughly the expected result:
function getSolarDeclination(){
return -23.44 * Math.sin( (360 / 365.25) * getDayOfYear() * Math.PI/180 )
}
function getDayOfYear(){
var now = new Date();
var start = new Date(now.getFullYear(), 0, 0);
var diff = now - start;
var oneDay = 1000 * 60 * 60 * 24;
var dayOfYear = Math.floor(diff / oneDay);
return dayOfYear + 284
}
console.log(getSolarDeclination())

Javascript setcookie()

The following line of code sets an event to happen only once per 24 hours, how do I make it occur every 12 or 6 hours? Thanks
setCookie(1, 24 * 60 * 60 * 1000);

JavaScript references time in milliseconds, and so therefore the equation 24 * 60 * 60 * 1000 is converting 24 hours into milliseconds (24 hours * 60 minutes in a hour * 60 minutes in a second * 1000 seconds in a millisecond).
Therefore, 12 hours would look like:
setCookie(1, 12 * 60 * 60 * 1000);
and 6 hours would look like:
setCookie(1, 6 * 60 * 60 * 1000);
and just for fun, 5 days would look like:
setCookie(1, 5 * 24 * 60 * 60 * 1000);

jquery date difference trouble

I made this little function from code snippets around the net. It does what its expected to do except that it decreased by 2 seconds every countdown tick instead of one, if i refresh the page it goes back to the original time again. Can you guys see what the problem is?
jQuery.countdown = function(selector, datevalue) {
var amount = datevalue*1000;
var curdate = new Date();
curdate = curdate.getTime();
var difference = amount - curdate;
if(amount < 0 || curdate >= amount){
$(selector).html("Done");
}
else{
datevalue--;
var daysRemaining = Math.floor(difference / 1000 / 60 / 60 / 24);
var hoursRemaining = Math.floor(difference / 1000 / 60 / 60 - (24 * daysRemaining));
var minutesRemaining = Math.floor(difference / 1000 / 60 - (24 * 60 * daysRemaining) - (60 * hoursRemaining));
var secondsRemaining = Math.floor(difference / 1000 - (24 * 60 * 60 * daysRemaining) - (60 * 60 * hoursRemaining) - (60 * minutesRemaining));
$(selector).html(daysRemaining+':'+hoursRemaining+':'+minutesRemaining+':'+secondsRemaining);
setTimeout(function() {
$.countdown(selector, datevalue);
}, 1000);
}
};
$.countdown('.date', 1332239568);

Remove datevalue--;
What you're doing now is to count down to a specific epoch time datevalue. But, you are decreasing it by one second each tick. Meanwhile, current time passes in setTimeout so you are both moving in time forward and pulling the target to yourself.
Either keep the original curdate of first call, saved somewhere. Or remove datevalue--;.

Calculate number of weeks , days and hours from milliseconds

There were many similar questions around but none addressed this calculation. Using javascript i it is easy to find the number of milliseconds diff b/w 2 dates for ex:
var mil = Math.floor(new Date("1/1/2012") - new Date("1/7/2012"))
mil is assigned 518400000
to get weeks i would do below
var weeks = mil / (1000*7*24*60*60);
in the above example it exactly fits 1 week. For other possible inputs i would like to get output as ex:
n Weeks, y days , z hours
So i did mil % (1000*7*24*3600) to get the modulus and from the remainder calculate number of days. but astonishingly this was answer i got from console
1 weeks , 6 days seems the week calculated before is also accounted for days again.
How should i calculate these correctly?

var seconds = (mil / 1000) | 0;
mil -= seconds * 1000;
var minutes = (seconds / 60) | 0;
seconds -= minutes * 60;
var hours = (minutes / 60) | 0;
minutes -= hours * 60;
var days = (hours / 24) | 0;
hours -= days * 24;
var weeks = (days / 7) | 0;
days -= weeks * 7;
Assuming mils is non-negative, this leaves mils in the range [0, 1000), leaves minutes and seconds in the range [0, 60), leaves hours in the range [0, 24), and leaves days in the range [0, 7).

There should be 6 days between them, not one week. Your weeks calculation needs to round down:
var weeks = Math.floor(mil / (1000 * 7 * 24 * 60 * 60));
Also, your milliseconds are negative; you want either
var mil = new Date("1/7/2012") - new Date("1/1/2012");
or
var weeks = Math.floor(Math.abs(mil) / (1000 * 7 * 24 * 60 * 60));