    # How to calculate hours between two dates JavaScript?

The specific part of the date or time value (year, month, or day, hour, minute, second, millisecond, or microsecond) that the function operates on. For more information, see Date parts for date or timestamp functions.

Specifically, DATEDIFF determines the number of date part boundaries that are crossed between two expressions. For example, suppose that you're calculating the difference in years between two dates,

``````select datediff(week,'2009-01-01','2009-12-31') as numweeks;

numweeks
----------
52
(1 row)``````
1 and
``````select datediff(week,'2009-01-01','2009-12-31') as numweeks;

numweeks
----------
52
(1 row)``````
2. In this case, the function returns 1 year despite the fact that these dates are only one day apart. If you are finding the difference in hours between two timestamps,
``````select datediff(week,'2009-01-01','2009-12-31') as numweeks;

numweeks
----------
52
(1 row)``````
3 and
``````select datediff(week,'2009-01-01','2009-12-31') as numweeks;

numweeks
----------
52
(1 row)``````
4, the result is 2 hours. If you are finding the difference in hours between two timestamps,
``````select datediff(week,'2009-01-01','2009-12-31') as numweeks;

numweeks
----------
52
(1 row)``````
5 and
``````select datediff(week,'2009-01-01','2009-12-31') as numweeks;

numweeks
----------
52
(1 row)``````
6, the result is 2 hours.

date|time|timetz|timestamp

A DATE, TIME, TIMETZ, or TIMESTAMP column or expressions that implicitly convert to a DATE, TIME, TIMETZ, or TIMESTAMP. The expressions must both contain the specified date or time part. If the second date or time is later than the first date or time, the result is positive. If the second date or time is earlier than the first date or time, the result is negative.

BIGINT

The following example finds the differences in number of hours, between a TIMETZ literal and timetz_val.

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• ### Time difference between two time fields on the same day

To calculate the difference between two time fields in hours, minutes, or seconds, use the following formula:

`getTimeDiff('{time_variable_2}', '{time_variable_1}', 'm');`

where time_variable_1 is the first time point (time field) and time_variable_2 is the second time point. Replace these with your own variable names.

You can also change the units of time:

• For hours: use 'h' instead of 'm'
• For seconds: use 's' instead of 'm'

Since time fields capture only hours and minutes, this difference will always be rounded to the nearest 60 sec.

Note: This formula is valid only if the two times are on the same date.

### Time difference between two time fields on two consecutive dates

If the two times are on two consecutive days, you can use one of the following calculations, depending on whether you want the outcome in hours, minutes, or both. This template requires the times to be filled in in a 24 hour format. This difference will be rounded to the nearest 60 sec.

There are so many things that you could do with a date & time calculator. With a date & time calculator, you can calculate how many days it may take for delivery to arrive, how many months it may take for a subscription to expire, or maybe you want to build your own time calculator like this Amazing App, name it …

In this article, I will show you how you can create a simple function that will help to calculate the difference between two dates.

LET’S BEGIN

I will call the function `calDate()` short for ‘calculateDate’.

This function will have 2 parameters which are `date1` and `date2` and these 2 dates must be in the format MM-DD-YYYY (Month-Day-Year), to avoid errors during calculation.

I love writing dates in the format DD-MM-YYYY, but in this article, I happen to not be in support of this guy 😅.

Now, let's start off with the function.

I will create a new instance of a`Date` object and find the timestamps of both dates

Next, we have to prevent negative values as we subtract a higher timestamp from a lower timestamp because this can ruin our result.

I will use a condition to check which timestamp is greater and then swap them, as you can see on line 18.

I have passed the result of subtracting timestamp 2 from timestamp 1 as an argument to a new date instance in order for JavaScript to convert the resulting timestamp to date.

Next, we have to retrieve the days, months, and years from the result and then join them with a hyphen. This will help us to convert it to an array that we will read from later.

If you observed the code above, you’ll notice that I added +1 to the `getMonth()` method.

This is because JavaScript counts months from a zero index, this means that 0 — 11 is January up to December, so

• 0 is for January
• 1 is for February
• up to 11 for December.

On line 26, I drafted how the array would look like, with the format DD-MM-YYYY, then on line 28, I used the split method to convert the draft to an array.

IT’S TIME TO READ FROM THE ARRAY

The array was created in this format:

• At position 0 is the Day
• At position 1 is the Month
• At position 2 is the Year

We will subtract each member of this array from the default date which is (01–01 -1970). This will help us know the number of days, months, and years that have elapsed.

We also need to set up a custom text that will help to prevent errors in counting like; 1 years ago or 1 months ago.

Now if you search for how many days there are in 6 months, you would get the formula that we will use to get the total number of days between the two dates.

## FINDING THE TOTAL NUMBER OF DAYS ELAPSED

Let’s find the total number of days by converting the years and months to days, then we will sum the result with the already existing days from the calculation.

IMPROVING THE CUSTOM TEXT

I will check if the number of years that have elapsed is equal to 1, then I will show the custom text as a year. For Eg 1 year.

But if the number of years that have elapsed is greater than 1, I will show the custom text as years. Otherwise, I will not show any value.

Note: I used a Tenary Operator to simplify the logic.

Let’s round off the total days to the nearest integer because there is a 95% possibility that the result will end up as a number with a decimal. I will use the math method `Math.round()` to achieve this, and then I will return the result as an object.

TESTING THE CODE

I will use the dates below:

• date 1 = today (m-d-y) = 11–19–2021
• date 2 = future (m-d-y) = 12–12–2026

This is the output:

We have 5 years and 23 days left till the 12th of December 2026.

Now if you use an external App like time and date for the same calculation, you should get if not approximate, the same value.

## EXTENDING THE CALCULATOR

Since we are able to calculate the total days that have elapsed, we can extend the calculator to calculate the;

• total number of seconds
• total number of minutes
• total number of hours and
• total number of weeks

So when I call the function to calculate the date difference between today (08–04–2022) and the same future date (12–12–2026), this is the result.

So from the calculation, we still have 4 years, 4 months & 10 days left till the 12th of December 2026.

CONCLUSION

So that’s a basic setup for a function that helps to calculate the difference between two dates.

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### How do you calculate the difference in hours between two dates?

Finding the number of hours or the time between two times/dates is simple, just subtract the start date/time from the end date/time and multiply the result by 24 hours.

### How to calculate number of hours in JavaScript?

JavaScript Code: function timeConvert(n) { var num = n; var hours = (num / 60); var rhours = Math. floor(hours); var minutes = (hours - rhours) * 60; var rminutes = Math. round(minutes); return num + " minutes = " + rhours + " hour(s) and " + rminutes + " minute(s)."; } console. log(timeConvert(200));

### How to get hour minute and second from the date () in JavaScript?

Display Hours, Minutes, and Seconds using JavaScript.
getHours() – This uses the today variable to display the current hour. This uses a 24-hour clock..
getMinutes() – Displays the current minute reading..
getSeconds() – Displays the current seconds reading..

### How do I calculate hours between two dates in typescript?

var hours = Math. abs(date1 - date2) / 36e5; The subtraction returns the difference between the two dates in milliseconds. 36e5 is the scientific notation for 60*60*1000 , dividing by which converts the milliseconds difference into hours. 