Okay then.
So a lot of the time when working with dates in JavaScript, whether that be storing them in a database
or maybe comparing dates together, it's a lot easier to use timestamps than using date objects directly.
So we saw in the last video that we could get a new date object by saying new date and using the date
constructor.
And if we wanted to get the timestamp from that date, we'd use the get time method.
And if we look at this, it looks like a long number and this is the number of milliseconds since 12
a.m. on the 1st of January 1970.
So then if we wanted to compare two dates together, we could compare these two time stamps together
to work out the difference in time between them, the difference in milliseconds.
Let me do an example.
What I'm going to do is say const before and set this equal to a new date object.
So now we have two date objects, but at the minute they're both essentially going to be the same because
when we say new date like this, it just creates a date, which is now.
But I want to create a date, which is sometime in the past.
Now, to create a date which is not now and is sometime in the past or sometime in the future.
Instead what we do is pass in some kind of string in here and then that is going to create that date
object based on that string.
Now, that string can be in several different formats.
I'm just going to type one of the formats in here.
So I'm saying February 1st, 2019, 730 in the morning.
So we're going to see other formats that we can write in here later on, but this is just one of them
and that is going to convert this into a new date object based on this date right here.
So what I'm first going to do is now log out as well before and I'm not going to do get time on it just
yet.
I'm just going to see what this date looks like.
And we can see right here Friday, Feb first, 2019 730.
So we get that date.
That's absolutely fine.
Now let's use the get time method to get the timestamp so we can see.
Now this is the number of milliseconds between the first of Jan 1970 and now, and this is the number
of milliseconds between the first of Jan 1970 and the before date.
So if we wanted to find out the difference in time between these two dates, what we could do is just
subtract this from this and then we're going to get the difference in milliseconds between those two
things.
So let me demo this.
I'm going to comment this out and then I'm going to say const diff for difference is equal to now dot
get time to get the milliseconds from now and minus before dot get time to get the milliseconds from
before.
Now I'm going to log this to the console console dot log and we'll log out the difference, save it
and preview and we can see this amount of milliseconds between these two dates.
So then now we have that difference in milliseconds.
What we could do is maybe convert these milliseconds into minutes or hours or days between these two
dates.
For example, we might have a blog on our website and it was created some time ago at this date, and
we have a timestamp for that date, which is right here.
We also have a timestamp for now, but what we want to do on our website is say this blog was created
maybe 20 days ago or 23 days ago, depending on the date.
So we can do that.
We can convert the difference in milliseconds that we have here into days, and then we could display
that on our web page.
So let's do this.
Let us now come down here and I'm going to say const mins is now equal to math dot round.
And then what we're going to do is pass in the difference in milliseconds, which is this we're going
to divide that by 1000, first of all, because there's 1000 milliseconds in a second.
So this is going to get us the amount of seconds.
Then I'm going to divide that by 60 and that gets us the amount of minutes.
So that is the difference between these two timestamps in minutes.
Now, I'm going to log this to the console console dot log and we'll say mins save it.
And we can see that right here.
Okay.
So that's the difference in minutes between these two dates.
Now let's do hours.
So let's change this to hours and change this to.
Men's over 60.
And what we're doing is dividing the number of minutes we have.
By 60 because the 60 minutes in an hour and that's getting us the amount of hours in between these two
things.
So let's log that to the console.
We'll say hours as well.
Save and preview.
And now we can see this thing right here.
That is the difference in hours between these two dates.
And finally, let's do the difference in days.
So I'll change this to days.
Then I'm going to say hours over 24 because there's 24 hours in a day.
And this will get us the difference in days between the two dates.
Save it.
And now we can see there's 47 days between these two dates.
So I can now say something like console dot log.
Then I'm going to use a template string and I'll just say the blog was written and then we're going
to output the number of days.
So curly braces and dollar sign, then days and we'll say a go.
So if I save it and refresh, we can see the blog was written 47 days ago, so this is something we
could potentially output in the browser underneath our blog when we have them.
And we do that by getting the timestamp of the blog, which could be stored in a database and comparing
it with the timestamp of now.
So that's a good use of timestamps.
Now imagine we're storing timestamps in a blog and we get those timestamps back and we don't necessarily
want to do any kind of comparison between dates right here.
And instead we just want to take that timestamp and convert it into an actual date object and then do
something with that date.
Well, we can do that.
Let me just do a little comment down here to say converting timestamps into date objects and then underneath
I'm going to say const timestamp is equal to some random number.
Now I'm just going to copy this number from my repo so I don't have to write it out again and paste
it in.
And this looks very much like a timestamp.
The number of milliseconds between a certain date and the 1st of June 1970.
So I get that now.
But this timestamp isn't a date object.
We can't do things like timestamp and then, you know, get the full year or get the day or anything
like that.
So we'd have to convert this now into a date object because at the minute it's just an integer, it's
just a number.
So the way we do that, and I'm going to log this to the console is by saying create a new date object
and then pass in the timestamp.
So when we pass in a number like this into the date object, it converts that timestamp into the date
object.
So if I save it and look over here, now we can see that full date logged to the console.
And now if we stored this in a constant, then we could do things like get the full year or get the
day, etcetera on that.
So there we go, my friends, that is timestamped.
It's something we probably will use in a future project or future lessons when we're working with dates.
