> For the complete documentation index, see [llms.txt](https://docs.cekat.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cekat.ai/api-documentation/formats.md).

# Formats

#### Phone numbers

Write phone numbers as digits only, starting with the country code and without `+` or a leading `0`, for example `6281234567890`.

#### Dates and times

Date filters accept a date (`start_date`, `end_date`) in `YYYY-MM-DD` format, or a date and time (`start_datetime`, `end_datetime`) in `YYYY-MM-DDTHH:mm:ss` format with an optional offset such as `+07:00` or `Z`. Use one or the other for each end of the range, not both.

Values without an offset are read in the time zone given by the `X-User-Timezone` header, an IANA name such as `Asia/Jakarta`. If you leave the header out, `Asia/Jakarta` is used.

Fields you send, such as `schedule_at`, use ISO 8601 with an offset, for example `2026-10-20T09:00:00+07:00`.

#### IDs

Most IDs are UUIDs, such as `0f9e8d7c-6b5a-4c3d-2e1f-0a9b8c7d6e5f`. WhatsApp template IDs (`wa_template_id`) are Meta's numeric IDs, sent as strings.