Recently, we had a lively conversation on the forum about date math in FileMaker Pro 16. During this conversation, I found that FileMaker's date math** **doesn't match standard date API results (documented below) I used to calculate the date 1 month in the future from Jan, 31, 2000.

**Here's what FileMaker gets (attempting date math directly with no CF):**

*Note: as others have pointed out below this date calculation approach above is "apples and oranges" to the methods described below. However, the goal, was to do date math for one month ahead of a date either directly (as the example above), without having to write a "CF", or using a built-in date function that abstracts that calculation....and get the same result as the standard date APIs below.*

Below are my other tests **(**nine of them using different methods)....all of which show that adding a month to 2000-01-31 gives **2000-02-29**, not, as FileMaker computes using the attempted direct date method above, 2000-03-02.

**Test 1 and Test 2 (two different API tests):**

Using Java, either the Java 8 DateTime API (LocalDate's "plusMonths()" method or the older Calendar class) gets:

**2000-02-29**

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**Test 3:**

Additionally, going to a website that lets you calculate a date in the future, when picking 1 month, from 2000-01-31, gave me **2000-02-29**:

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**Test 4:**

Also, Excel, using the **EDATE** function to add 1 month to 2000-01-31 gave me .... **2000-02-29**:

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**Test 5:**

Using Apache's DateUtils common library, static method addMonths: DateUtils.addMonths() method gave me.... **2000-02-29**

**(DateUtils (Commons Lang 2.6 API))**

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**Test 6:**

Using Python's DATE API, we also got **2000-02-29** as one month from 2000-01-31.

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**Test 7: Visual FoxPro**

**returns...**

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**Test 8: JavaScript's "Adjust" function**

**returns: 02-29-2000**

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This seem consistent FileMaker behaviour

The February after that January has 29 days

So the 30th day of moth 2 is the date 30 days after the 1st of the second month

and consequently the 31st day of the month is 31 days after the 1st of the month, which will completely be the 2nd of the 3rd month.

It depends how you interpret 'a month later' - do you literally mean if its past the 28th and then next month is February then give me the last dat of the month or give me 28 days from this point.

In the same way that FIleMaker treats dates since 01/01/01 and not some other arbitrary date in 1970 this is documented and how the maths, thats maths not math, works. I fully accept that this may be slightly different to other external things but there is no reason why these cant co-exist.

SQL needs insert dates in Zulu format. We know that. We convert Filemaker timestamps to Zulu. Its the same thing, we know about a difference and handle it.