date calculator

How to calculate date to date or date of birth using Javascript?

Learn the formula. Here are 2 JavaScript methods given below to calculate age or date to date.

Important: here is perfect formula of date calculate. nowadays, many websites and applications using this formula.

Best and accurate Age Calculate Formula in Javascript

Here, Birth Date Calculator in Javascript [formula 1, calculations method]
<script> function calculateAge(birthDate) { const today = new Date(); const ageInMilliseconds = today - birthDate; const years = Math.floor(ageInMilliseconds / (1000 * 60 * 60 * 24 * 365.2422)); const monthsInMilliseconds = ageInMilliseconds % (1000 * 60 * 60 * 24 * 365.2422); const months = Math.floor(monthsInMilliseconds / (1000 * 60 * 60 * 24 * 30.4368)); const daysInMilliseconds = monthsInMilliseconds % (1000 * 60 * 60 * 24 * 30.4368); // Calculate the number of days in the remaining milliseconds. const days = Math.floor(daysInMilliseconds / (1000 * 60 * 60 * 24)); return { years, months, days }; } const birthDate = new Date("1996-06-03"); const age = calculateAge(birthDate); alert("Your age : "+age.days+" days, "+age.months+" months, "+age.years+" years") </script>

Here's a concise explanation of the code:

Function Breakdown:


    • Takes a birth date as input.
    • Calculates the age in years, months, and days.
    • Returns an object containing those values.


    • Gets today's date
    • Calculates age in milliseconds (difference between today and birth date)
    • Divides milliseconds into:
      • Years: using average days per year (365.2422)
      • Months: using remaining milliseconds and average days per month (30.4368)
      • Days: using remaining milliseconds
    • Returns an object with years, months, and days values

Example Usage:

  1. Sets a birth date
  2. Calls calculateAge to get the age
  3. Displays the age in a message

Key Points:

  • Uses milliseconds for accurate time calculations.
  • Approximates years and months based on average days.
  • Returns a structured object for easy access to age components.

Birth Date Calculator in Javascript [formula 2 ,IF Method ]

<script> today = new Date() ; birth = new Date("1996-06-03"); years = today.getFullYear() - birth.getFullYear(); months= today.getMonth() - birth.getMonth(); days= today.getDate() - birth.getDate(); if(days<0){months-=1;days+=30;} if(months<0){years-=1;months+=12;} alert("IF formula "+days+":"+months+":"+years) </script>

Here's a short explanation of the code:

1. Sets dates:

  • Stores today's date in a variable named today.
  • Creates a date object called birth for the date "1996-06-03".

2. Calculates age differences:

  • Subtracts the birth year from the current year to get years.
  • Subtracts the birth month from the current month to get months.
  • Subtracts the birth day from the current day to get days.

3. Adjusts for negative differences:

  • If days is negative (meaning the current day is before the birth day in the month), it subtracts 1 from months and adds 30 to days to account for the month boundary.
  • If months is negative (meaning the current month is before the birth month), it subtracts 1 from years and adds 12 to months to account for the year boundary.

4. Displays results:

  • Uses an alert box to display the calculated age in the format "days:months:years".

Key points:

  • The code calculates age based on full years, months, and days, not just total days alive.
  • It handles cases where the current day or month is before the birth day or month.
  • It uses the Date object and its methods for date manipulation.

Click here to explore our Age calculate tool Age calculator

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