[Vuejs]-Erorr api post vue laravel

You are correct. Whenever the axios instance receives a response with a statuscode out of the range of 2xx it will throw an error. Reference

You can implement your functionality using the code below.

async inputschedule(){
  await axios.post('api/schedule',{
    tweet:this.text,
    schedule_at:this.data+' '+this.clock
  })
  .then((response) => {
    // Handle success response.
  }
  .catch((error)=>{
    // Check whether the response was received.
    if (error.response) {
      if (error.response.status == 400){
        console.log(error.response.status)
        this.error='Il post non può essere pianificato per questa data'
      }
    }
  })
},