# isMonthStart {#ismonthstart}

**Parent topic:**[Functions](../../Functions/category.md)

## Syntax {#syntax}

`isMonthStart(X)`

## Arguments {#arguments}

**X** is a scalar/vector of type DATE, DATEHOUR, DATETIME, TIMESTAMP or NANOTIMESTAMP.

## Details {#details}

Determine if each element in *X* is the first day of a month.

## Examples {#examples}

```
isMonthStart(2012.05.01);
// output: true

isMonthStart([2012.05.01,2012.05.02]);
// output: [true,false]
```

Related function: [isMonthEnd](isMonthEnd.md)

