Month wrong beginning

Hi!

My graph starts with the 2nd of month and not the first day. I have to shift the range back to -1d to get the first day of the month included. Am I doing something wrong?

import "timezone"

option location = timezone.location(name: "Europe/Vienna")

from(bucket: "weather")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["_measurement"] == "weather")
  |> filter(fn: (r) => r["_field"] == "drain_piezo")
  |> aggregateWindow(every: v.windowPeriod, fn: max, createEmpty: false)
  |> map(fn: (r) => ({Time: r._time, "DailyRain": r._value}))
  |> yield(name: "DailyRain")

Thanks!