# Moment-timezone import / duplication trap

**URL:** <https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041>\
**Category:** Ask the community\
**Created:** [September 22, 2025, 12:36pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041 "2025-09-22T12:36:34Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![ole.sorheim](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/ole.sorheim/32/3168_2.png) [@ole.sorheim](https://community.appfarm.io/u/ole.sorheim)\
**Post date:** [September 22, 2025, 12:36pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/1 "2025-09-22T12:36:34Z")

</div>

chatgpt is telling me i have run into the classic **moment-timezone import / duplication** trap

Im getting the error: **moment.tz is not a function**  
Here’s the relevant code:

```auto
const TZ = 'Europe/Oslo';
const startMonth = moment.tz(dateTimeValue, TZ).startOf('day');
const endMonth = moment.tz(periodEnd, TZ).endOf('day');
const startUnit = moment(historikkEnhet.fra).tz(TZ).startOf('day');
const endUnit = moment(historikkEnhet.til).tz(TZ).endOf('day');

```

The code ran once without error, but now im consistently getting the error. Anyone experienced this and know how ti fix it?

---

<div class="post-metadata">

**Author:** ![Simona](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/simona/32/201_2.png) [@Simona](https://community.appfarm.io/u/Simona)\
**Post date:** [September 22, 2025, 2:42pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/2 "2025-09-22T14:42:39Z")

</div>

Hi @ole.sorheim,

I tried to reproduce the issue, but everything worked on my side. Could you double-check that the correct library is added? Just a quick reminder: the returned moment.js object needs to be converted into a Datetime data type, which you can do by calling `.toJSON()`.

This is how I tested:

 ![image](https://europe1.discourse-cdn.com/flex013/uploads/appfarm/original/2X/8/87a42cb3ff453f59b3f65ed4889f9bb8a58644ab.png)

---

<div class="post-metadata">

**Author:** ![ole.sorheim](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/ole.sorheim/32/3168_2.png) [@ole.sorheim](https://community.appfarm.io/u/ole.sorheim)\
**Post date:** [September 22, 2025, 6:01pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/3 "2025-09-22T18:01:24Z")

</div>

I used the Moment.js package, not Moment Timezone since it is Deprecated.  
When using Moment.js I ran into several problems like the one above. All of these failed:  
moment.min()  
moment.max()  
moment.tz()

In the function editor, it looks like all these functions exist. However, running the function fails with the error “moment. (…) is not a function”

---

<div class="post-metadata">

**Author:** ![Simona](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/simona/32/201_2.png) [@Simona](https://community.appfarm.io/u/Simona)\
**Post date:** [September 24, 2025, 2:28pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/4 "2025-09-24T14:28:15Z")

</div>

Hi @ole.sorheim,

I double-checked how moment works inside Appfarm Create functions, and here’s the key point:

- When you call `moment(...)` in a function, the App Time Zone is applied automatically. That means you don’t need (and can’t) call `.tz(...)` yourself.

- There was a short period (around version 113, earlier this year) where `.tz(...)` looked like it worked, but that was actually a bug. It’s not supported anymore.

So your snippet should look like this instead:

```javascript
const startMonth = moment(dateTimeValue).startOf(‘day’).toJSON();
const endMonth = moment(periodEnd).endOf(‘day’).toJSON();
const startUnit = moment(historikkEnhet.fra).startOf(‘day’).toJSON();
const endUnit = moment(historikkEnhet.til).endOf(‘day’).toJSON();

```

If you really need manual timezone conversion different from the app’s timezone, update the app time zone under app variables as described [here](https://docs.appfarm.io/reference/platform-concepts/date-and-time#default-behavior).

Regarding min/max: Only the instance methods (a.max(b), a.min(b)) are supported.

```javascript
const a = moment("2025-09-01T10:00:00");
const b = moment("2025-09-05T15:00:00");

const latest = a.max(b); 
const earliest = a.min(b);

return latest.toJSON();

```

Hope this clears it up!

---

<div class="post-metadata">

**Author:** ![ole.sorheim](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/ole.sorheim/32/3168_2.png) [@ole.sorheim](https://community.appfarm.io/u/ole.sorheim)\
**Post date:** [September 24, 2025, 2:52pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/5 "2025-09-24T14:52:36Z")

</div>

Thanks!

Still have some questions. First why do you need .toJSON() ? Im not using it anywhere and the solution seems to work just fine. See the relevant parts of the code below:

```auto
const startMonth = moment(dateTimeValue); // e.g. "2025-07-31T22:00:00.000Z" (Aug 1, 00:00 Oslo)
const endMonth = moment(periodEnd); // e.g. "2025-08-31T21:59:59.000Z" (Aug 31, 23:59:59 Oslo)

const startUnit = moment(historikkEnhet.fra);
const endUnit = moment(historikkEnhet.til);

// Clamp to the income month
const actualStart = startUnit.isAfter(startMonth) ? startUnit : startMonth;
const actualEnd = endUnit.isBefore(endMonth) ? endUnit : endMonth;

if (actualEnd.isBefore(actualStart)) return 0;
const msPerDay = 24 * 60 * 60 * 1000;
const daysUnit = actualEnd.diff(actualStart, 'days');
const weeksUnit = parseFloat(((daysUnit + 1) / 7).toFixed(5));
const daysMonth = endMonth.diff(startMonth, 'days');

```

---

<div class="post-metadata">

**Author:** ![Simona](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/simona/32/201_2.png) [@Simona](https://community.appfarm.io/u/Simona)\
**Post date:** [September 24, 2025, 3:18pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/6 "2025-09-24T15:18:27Z")

</div>

Hi @ole.sorheim,

We recommend using `.toJSON()` as outlined in the [documentation](https://docs.appfarm.io/reference/platform-concepts/date-and-time#function-editor-and-moment.js) to ensure the value is converted to the correct data type. While it may sometimes work without it, as you mentioned, skipping it can lead to issues. For example, in the min/max case, omitting `.toJSON()` results in this type of error:

 ![image](https://europe1.discourse-cdn.com/flex013/uploads/appfarm/original/2X/0/0fb4c39f2cbcf1c23d49075d88a9cb4ae28ae574.png)

---

<div class="post-metadata">

**Author:** ![ErikAKSkallevold](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/erikakskallevold/32/1378_2.png) [@ErikAKSkallevold](https://community.appfarm.io/u/ErikAKSkallevold)\
**Post date:** [September 25, 2025, 10:37am UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/7 "2025-09-25T10:37:26Z")

</div>

To add to this, `toJSON()` is only required when returning a Moment value from a function. This is to ensure that the output of the function is a primitive value and not an object.

---

<div class="post-metadata">

**Author:** ![ole.sorheim](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/ole.sorheim/32/3168_2.png) [@ole.sorheim](https://community.appfarm.io/u/ole.sorheim)\
**Post date:** [October 2, 2025, 11:14am UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/8 "2025-10-02T11:14:30Z")

</div>

> [@Simona](#):
>
> Regarding min/max: Only the instance methods (a.max(b), a.min(b)) are supported.

I’m getting messages saying that the instance methods are depricated.  
Im also getting som funny results using these.

This aint right is it?

```auto
a = 2025-10-29T23:00:00.000Z
b = 2025-09-30T22:00:00.000Z
a.max(b) = b ???

```

```auto
    console.log("Before max()", temp_start, actualStart)
    temp_start = temp_start.max(actualStart)
    console.log("After max()", temp_start, actualStart)

```

a.max() seem to consistently return the object furthest back (i.e. how I would expect min() to work)

 ![image](https://europe1.discourse-cdn.com/flex013/uploads/appfarm/original/2X/3/3ee309e68b6e5fd734ccc4e59988d17a6ca7fddc.png)

 ![image](https://europe1.discourse-cdn.com/flex013/uploads/appfarm/original/2X/4/4e174555aab00a5a9eb132d17ba4a46a9d5c972a.png)

---

<div class="post-metadata">

**Author:** ![ole.sorheim](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/ole.sorheim/32/3168_2.png) [@ole.sorheim](https://community.appfarm.io/u/ole.sorheim)\
**Post date:** [October 2, 2025, 11:22am UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/9 "2025-10-02T11:22:11Z")

</div>

Did some further testing, and the only thing I got to work is the following:

```auto
temp_start = temp_start.max(temp_start, actualStart)

```

This seems very counterintuitive. Is this intended?

I can also add that I’m 99% sure this was not how it worked yesterday. Is it maybe related to some update? I was prompted to update in Create today

---

<div class="post-metadata">

**Author:** ![kristian](https://dub1.discourse-cdn.com/flex013/user_avatar/community.appfarm.io/kristian/32/58_2.png) [@kristian](https://community.appfarm.io/u/kristian)\
**Post date:** [October 2, 2025, 12:48pm UTC](https://community.appfarm.io/t/moment-timezone-import-duplication-trap/2041/10 "2025-10-02T12:48:47Z")

</div>

Hi!

I believe you first try was incorrect use of max(). This is defined here:

> **[Moment.js | Docs](https://momentjs.com/docs/#/get-set/max/)**

temp\_start = temp\_start.max(actualStart) always return actualStart, since you need to put the dates inside the paranthesis.

Hope that helps (and is the reason). This is not behaviour defined by Create, but by the momentjs library.