# T408

> indicator on a calendar timeframe

**Severity** Error

A `ta.*` indicator receives a series from a subscription on a calendar timeframe (`1M`). Months have different lengths, so period-based indicators would weigh them inconsistently.

Run the indicator on a fixed-length timeframe (seconds to weeks), or read the monthly values directly without an indicator.

## Failing example

```flowscope
script "Monthly EMA"
data monthly = subscribe(data.ohlcv, timeframe: 1M)
plot ema = plot.line(title: "Monthly EMA 12", style: linestyle.step)
on monthly.close {
  ema.plot(ta.ema(monthly.close, 12))
}
```

## Fixed example

```flowscope
script "Monthly EMA"
data weekly = subscribe(data.ohlcv, timeframe: 1W)
plot ema = plot.line(title: "Weekly EMA 52", style: linestyle.step)
on weekly.close {
  ema.plot(ta.ema(weekly.close, 52))
}
```

## Related

- [T111](/docs/scripting/reference/diagnostics/t111)
- [T403](/docs/scripting/reference/diagnostics/t403)