Schedules a broadcast to an audience filter (the same filter as POST /v1/messaging/broadcast/audience). When it sends is schedule: at is a wall-clock time with NO offset (e.g. 2026-10-05T09:00), read in timezone (an IANA zone such as America/New_York). Add a recurrence (daily / weekly / monthly) to repeat it — at is then the first send and the time of day of every send. The audience is evaluated at every send, so contacts who join or leave your groups before then are included or excluded accordingly.

schedule.sendByLocalTime delivers at at's wall-clock time in each recipient's own timezone; it cannot be combined with waveConfig. A send that cannot start within 1 hour of its time is not sent.

Rate limit: 10 requests per minute, shared with update and cancel.