# What Is the Cheapest Day to Book KLM Flights? Expert Guide 2025 with Fly Dreamz

> Learn when is the cheapest time to book KLM flights and how flexible dates can help you save more. This guide explains trends, fare patterns, and tools to find the best offers for 2025. Visi more: https://www.flydreamz.com/blog/cheapest-day-to-book-klm-flights.aspx

- Host: Fly Dreamz
- Duration: 15 min
- Location: Cal Video
- Host time zone: America/Chicago
- Confirmation: Bookings are confirmed instantly.
- Booking page: https://cal.com/flydreamz/what-is-the-cheapest-day-to-book-klm-flights-expert-guide-2025
- Event type id: 4015997

## Check availability

```http
GET https://api.cal.com/v2/slots?eventTypeId=4015997&start=YYYY-MM-DD&end=YYYY-MM-DD&timeZone=<IANA time zone>
cal-api-version: 2024-09-04
```

The response is `{"data":{"YYYY-MM-DD":[{"start":"<ISO 8601 with offset>"}]}}`; no API key is needed.

## Book

```http
POST https://api.cal.com/v2/bookings
cal-api-version: 2026-02-25
Content-Type: application/json

{
  "eventTypeId": 4015997,
  "start": "<UTC ISO 8601 start from the slots response>",
  "attendee": {
    "name": "…",
    "email": "…",
    "timeZone": "<IANA time zone>"
  },
  "guests": [
    "guest@example.com"
  ],
  "bookingFieldsResponses": {
    "notes": "…"
  }
}
```

- Required fields: `name` (Your name), `email` (Email address)
- Optional fields: `notes` (Additional notes), `guests` (Add guests)
- `name` and `email` go in `attendee` and `guests` is a list of emails; every other field goes in `bookingFieldsResponses` under its name.