Calculating the number of days between two dates in JavaScript required to use date object for any kind of calculation. For that, first, get the internal millisecond value of the date using the in-built JavaScript **getTime() function**. As soon as both the dates get converted, proceed further by subtracting the later one from the earlier one which in turn returns the difference in milliseconds. Later, the final result can be calculated by dividing the difference (which is in milliseconds) of both the dates by the number of milliseconds in one day.

**Syntax:**

Date.getTime()

**Approach 1:**

- Define two dates using
**new Date()**. - Calculate the time difference of two dates using
**date2.getTime() – date1.getTime();** - Calculate the no. of days between two dates, divide the time difference of both the dates by no. of milliseconds in a day
**(1000*60*60*24)** - Print the final result using
**document.write()**.

**Example 1:** The following JavaScript program will illustrate the solution

`<script type = ` `"text/javascript"` `>` ` ` `// JavaScript program to illustrate ` ` ` `// calculation of no. of days between two date ` ` ` ` ` `// To set two dates to two variables` ` ` `var` `date1 = ` `new` `Date(` `"06/30/2019"` `);` `var` `date2 = ` `new` `Date(` `"07/30/2019"` `);` ` ` `// To calculate the time difference of two dates` `var` `Difference_In_Time = date2.getTime() - date1.getTime();` ` ` `// To calculate the no. of days between two dates` `var` `Difference_In_Days = Difference_In_Time / (1000 * 3600 * 24);` ` ` `//To display the final no. of days (result)` `document.write(` `"Total number of days between dates <br>"` ` ` `+ date1 + ` `"<br> and <br>"` ` ` `+ date2 + ` `" is: <br> "` ` ` `+ Difference_In_Days);` ` ` `</script>` |

**Output:**

Total number of days between dates Sun Jun 30 2019 00:00:00 GMT-0700 (Pacific Daylight Time) and Tue Jul 30 2019 00:00:00 GMT-0700 (Pacific Daylight Time) is: 30

**Approach 2:**

- Defined the present date by using the new
**date()**which will give the present date and the Christmas date by**date.getFullYear()**(this will get the year, 0-11 are the months in JavaScript). - if condition in order to calculate the total number of days if the Christmas has been passed already (this will calculate the no. of days between the present date and the Christmas of the next year).
- Use
**Math.round(christmas() – present_date.getTime())**Divided one day’s miliseconds to Calculate the result in milliseconds and then converting into days

**Example 2:** This example we calculated the number of days until Christmas day.

`<script type = ` `"text/javascript"` `>` ` ` ` ` `// One day Time in ms (milliseconds)` ` ` `var` `one_day = 1000 * 60 * 60 * 24` ` ` `// To set present_dates to two variables` `var` `present_date = ` `new` `Date();` ` ` `// 0-11 is Month in JavaScript` `var` `christmas_day = ` `new` `Date(present_date.getFullYear(), 11, 25)` ` ` `// To Calculate next year's Christmas if passed already.` `if` `(present_date.getMonth() == 11 && present_date.getdate() > 25)` ` ` `christmas_day.setFullYear(christmas_day.getFullYear() + 1)` ` ` `// To Calculate the result in milliseconds and then converting into days` `var` `Result = Math.round(christmas_day.getTime() - present_date.getTime()) / (one_day);` ` ` `// To remove the decimals from the (Result) resulting days value` `var` `Final_Result = Result.toFixed(0);` ` ` `//To display the final_result value` `document.write(` `"Number of days remaining till christmas <br>"` ` ` `+ present_date + ` `"<br> and <br>"` ` ` `+ christmas_day + ` `" is: <br> "` ` ` `+ Final_Result);` ` ` `</script>` |

**Output:**

Number of days remaining till christmas Sun Jun 30 2019 11:33:51 GMT-0700 (Pacific Daylight Time) and Wed Dec 25 2019 00:00:00 GMT-0800 (Pacific Standard Time) is: 178