Why Flux UI Ignored My Date Format (And How I Fixed It)

My app has charts on the dashboard and reports pages showing campaign performance over time. The x-axis labels were showing raw dates like 2025-01-01, 2025-02-01 — not exactly user-friendly. I wanted month names instead.

What should have been a simple formatting change took three attempts to get right. The reason? A Flux UI prop that silently does nothing depending on how your chart is configured.

Table of contents

What I was trying to do

The charts show monthly data over a 6-month period (never more than 12 months). I asked:

“I’d like to update the date formatting in all chart components to display full month names (e.g., ‘January’, ‘February’) instead of yyyy-mm-dd format… goals are 6 months by default, but never more than 12 months, hence no need to have the year. do you agree with this change?”

The recommendation was to use short month names (Jan, Feb, Mar) rather than full names — they take up less space on the x-axis and avoid labels overlapping on smaller screens.

Simple enough. But getting there was not straightforward.

Attempt 1: Change the format prop (didn’t work)

The chart was using a Flux UI component with a :format prop:

<flux:chart.axis axis="x" field="date"
  scale="categorical" :format="['month' => 'long']" />

The obvious fix was to change 'long' to 'short':

<flux:chart.axis axis="x" field="date"
  scale="categorical" :format="['month' => 'short']" />

This did nothing. The dates still showed as 2025-01-01.

Why it failed: When scale="categorical" is set, Flux UI displays the data values exactly as-is — raw strings. The :format prop is silently ignored. No error, no warning. It just does nothing.

Attempt 2: Remove the categorical scale (made it worse)

The next idea was to remove scale="categorical" so the chart would auto-detect the dates and use a time scale, which does respect the :format prop:

<flux:chart.axis axis="x" field="date"
  :format="['month' => 'short']" />

This sort of worked — the month names appeared — but the labels were wrong. Instead of showing one label per month (Jan, Feb, Mar, Apr, May), the time scale interpolated intermediate ticks and showed repeated labels like “Jan, Jan, Jan, Feb, Feb, Mar…”

“but if daily data why are there only 4 or 5 months, not 30/31 for every day of the month?”

The explanation: the data has one point per month (daily data is aggregated into monthly totals by the backend). But the time scale sees ISO date strings, interprets them as points on a continuous timeline, and generates its own tick marks between them. With only 5-6 data points spread across months, it fills the gaps with duplicates.

Attempt 3: Format the data in PHP (the fix)

The solution was to stop trying to format dates in the template and instead format them in PHP before they reach the chart.

The app uses a ChartDataService that builds the chart data arrays. This is where the date format was set:

// Before: raw ISO date
'date' => $monthDate->format('Y-m-d'),

// After: short month name
'date' => $monthDate->format('M'),

With the data already formatted as “Jan”, “Feb”, “Mar”, the categorical scale displays it correctly — because it’s just displaying strings as-is, which is exactly what we want.

The template was simplified by removing the :format prop entirely:

<!-- Before -->
<flux:chart.axis axis="x" field="date"
  scale="categorical" :format="['month' => 'long']" />

<flux:chart.tooltip.heading field="date"
  :format="['month' => 'long']" />

<!-- After -->
<flux:chart.axis axis="x" field="date"
  scale="categorical" />

<flux:chart.tooltip.heading field="date" />

The same change was needed in the Chart.js components (the app uses both Flux UI and Chart.js for different charts):

// Before
$monthLabel = $currentDate->format('F');  // "January"

// After
$monthLabel = $currentDate->format('M');  // "Jan"

Why it works this way

Flux UI’s scale prop fundamentally changes how the x-axis behaves:

The mismatch was using scale="categorical" (which treats values as strings) with :format (which only works on parsed dates). The two features don’t talk to each other.

Once you understand this, the rule is simple:

• Categorical scale → format your data in PHP/backend
• Time scale → let the :format prop handle it in the template

Carbon date format codes

If you’re formatting dates in PHP with Carbon (which Laravel uses by default), here are the codes that matter:

For charts showing 6-12 months of data, 'M' (short month) is usually the best choice — compact enough to avoid overlapping labels.

Where the data actually comes from

Understanding this fix required understanding how my chart data flows. The app has a ChartDataService that:

1. Pulls daily data from the database
2. Groups it by month and sums the values into monthly totals
3. Builds an array with date, actual, and forecast fields
4. Strips leading months with zero values (keeping at least two)
5. Calculates a linear forecast from the current average to the target

The date field in step 3 is where the formatting happens. By the time this data reaches the Blade template, it’s just an array of objects — the template shouldn’t need to know anything about date parsing.

This is actually a good pattern. Formatting data in the backend keeps your templates simple and avoids surprises from frontend libraries interpreting your data differently than you expect.

Key takeaway

When a prop silently does nothing, the problem is usually a mismatch between two settings. In Flux UI, scale="categorical" and :format don’t work together — categorical treats everything as raw strings. The fix is to format your data in PHP before it reaches the chart. This is also the more robust approach: your templates stay simple, and you don’t depend on the frontend library to parse and reformat your data correctly.