Child Spacing Calculator + Online Solver With Free Steps

The Child Spacing Calculator finds the exact time difference between two given dates of the form: time, day, month, and year. The calculator accepts a variety of time formats. 

The calculator can also be used to find the exact time it would be if you have an initial time instance and add a certain amount of time to it. For example, you can find the time exactly 23 days, 3 hours, and 30 minutes from today (see Example 2).

What Is the Child Spacing Calculator?

The Child Spacing Calculator is an online tool that calculates the period between two given time instances in a variety of formats. 

The calculator interface consists of two unlabeled text boxes separated by the word “to.” In the first box (top one before “to”), you enter the earlier time instance and the later time instance in the second one. The results incorporate the effect of leap years (one additional day per leap year’s February).

You can swap which time instance goes into which box; the result will be the same. However, some result sections like the calendar might not show or function correctly.

If you use the calculator for anything other than finding the difference between two dates, be careful with your input. Use the calculator’s “input interpretation” section from the results to verify that it works as intended.

Supported Time Formats

The calculator supports only the following time formats:

  1. 24/12 hour HMS format: The calculator uses the 24-hour format if “am/pm” is not designated, so “16:12:30” means 4:12:30 pm. The 12-hour format is used if am/pm is present, so “2:30:15 pm” is a valid input. 
  2. X hours, Y minutes, Z seconds: This is useful when adding a time value to a given date or date and time. For example, entering “4 hours, 12 minutes, 30 seconds” in the first box and “Jan 19, 1991” in the second would give the result: 7:47:30 pm Jan 18, 1991.

How To Use the Child Spacing Calculator?

You can use the Child Spacing Calculator to find the age difference given two birth dates by simply entering the dates into the text boxes. Let us assume we have two birth dates: September 18, 1999, and September 15, 2000. Note that all entries below should be placed without the quotes.

Step 1

Enter the earlier birth date into the first text box. In our case, we enter “September 18, 1999,” but we could also type “18 Sep 1999” or “Sep 18, 1999” or even “1999 Sep 18”; they all mean the same thing to the calculator.

Step 2

Enter the later birth date into the second text box. In our case, we enter “September 15, 2000.” Again, we can enter the date, month, and year in any order or format.

Step 3

Press the Submit button to find the time difference between the two and thus receive the age difference.


The result is the exact value of the difference starting from the largest units (years) to the smallest (months). For our example, it is “11 months 28 days,” or 363 days. 

Note that the calculator uses the following to signal a year (both common and leap):

1 year = 11 months and 31 days  

With the above formula, we would expect the answer to be 362 days because there is a three-day difference between the two dates and 365 days in a common year. However, the year 2000 was a leap year, and the month of February is between the two entries. 

Therefore, one additional day adds to the result, and one should interpret it as 11 months and 28 days of a leap year, which has 366 days instead of 365 in a common year. Then, 363 is the correct result.

Additional Sections

Several additional sections are also present in the result:

  • Input Interpretation: The input as the calculator understands it. It helps check that the calculator has interpreted the input entries as you intended.
  • Time Span: The same result in various combinations of units and singular units such as only in days, hours, minutes, seconds, etc. 
  • Calendar: If the month difference between the two entries is less than or equal to two months, then a calendar with the days past highlighted is also shown.
  • Time Difference From Today: The exact time difference of each entry from the current date. This section does not appear if the inputs contained the time of day (e.g., “15 sep 2000 1:30 am”) because of time-zone differences.
  • Notable Events Between Date 1 and Date 2: These are some interesting facts or events that took place in the period between the two dates.

Other sections may appear as well.

Solved Examples

Example 1

Alice’s birthday is 11th February 1990, and her brother Thomas’ birthday is 14th December 1993. What’s the difference in their age in terms of days?


The difference in terms of years, months, and days is 1993-1990 = 3 years, 12-2 = 10 months, and 14 – 11 = 3 days. 

1992 was a leap year. Considering that Thomas was born 365-(31-14)=348 days into 1993, we have 348+366+365 = 1079 days up to the start of 1991. Alice was born 31+11 = 42 days into 1990, so that is an additional 365-42=323 days for 1990, so:

1079+323 = 1402 days

Example 2

What day would it be 3 weeks and 2 days from January 15th, 2000?


The manual calculations are prone to human error, and you would need to look up a calendar. You can use the calculator instead by typing “3 weeks 2 days” in the first text box and “Jan 15, 2000” in the second, and you will get the date December 23rd, 1999, and that it was a Thursday.

Manual Date Verification

3 weeks = 21 days

$\Rightarrow$ (21 + 2) days = 23 days

The month of December has 31 days, so 15 days before January 15th would be December 31st, 1999. So the date = 31-(23-15) = 31-8 = 23, which means that the date is December 23rd, 1999. 

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