Hi @nattzp @evan-brass , I have been tinkering with my Hue bulb lately and found out how to create schedules.

The GATT UUID is 9da2ddf1‑0001‑44d0‑909c‑3f3d3cb34a7b (handle 0x0072), which is used to create a new schedule but also to activate/deactivate and delete existing schedules. I'll describe in detail my findings in the following.

I have created this Python script to manage and create schedules as an example.

List schedules

Listing schedules is a short query, not a full-body payload. You just want to send 0x00 to the GATT, and you'll receive a response like:

00 00 <unknown_or_status> <count> <id0_le> <id1_le> ...

Example response:

00 00 07 02 01 00 04 00

Common Full Schedule Payload Layout

Create and update operations both use the same full schedule-body format.

Confirmed byte layout:

Offset	Size	Meaning	Status
0	1	Operation opcode 01	confirmed
1..2	2	Source schedule id, little-endian. ff ff for create, existing id for update	confirmed
3	1	Constant 00 in captured create/update payloads	confirmed
4	1	Enabled flag in update flows. 01 for active, 00 for disabled	confirmed
5	1	Constant 00 in captured create/update payloads	confirmed
6..9	4	Semantic schedule timestamp, little-endian Unix time	confirmed
10..13	4	Fixed bytes 00 0e 01 01 for standard wake/sleep payloads	confirmed for standard wake/sleep
14	1	Schedule kind marker: 00 sleep, 01 wake	confirmed
15..22	8	Type-specific fixed block identifying the schedule behavior	confirmed as fixed per kind
23..24	2	Fade duration in deciseconds, little-endian	confirmed
25..26	2	Type/title-derived field. For standard payloads this matches 0x0118 + title_len	confirmed for standard wake/sleep builder
27..42 in early notes / 28..43 in opcode-included payloads	16	Schedule UUIDv4 bytes	confirmed
43 in early notes / 44 in opcode-included payloads	1	Type-specific flag. 01 for captured sleep schedules, 00 for captured wake schedules	confirmed by capture, semantics inferred
next 4 bytes	4	Constant recurrence/sentinel field ff ff ff ff	confirmed
next 1 byte	1	ASCII title length	confirmed
next N bytes	N	ASCII schedule title	confirmed
final byte	1	Enabled state in stored/read-back payloads and update flows	confirmed

Important timestamp rule:

• Sleep schedules store the visible selected sleep time directly.
• Wake schedules store the fade-start time, not the visible wake completion time.

Important type-specific fixed blocks for standard payloads:

Schedule kind	Fixed bytes at 10..22	Meaning
sleep	00 0e 01 01 00 02 01 01 03 02 4c 02 05 02	standard go-to-sleep payload prefix
wake	00 0e 01 01 01 02 01 fe 03 02 bf 01 05 02	standard wake-up payload prefix

Create A New Schedule

Create uses the full schedule-body format with a source id of ffff.

Generic create payload shape:

01 ff ff 00 01 00 <timestamp_le> <type_specific_bytes> <fade_ds_le> <field_25_26> <uuid16> <kind_flag> ff ff ff ff <title_len> <title_ascii> 01

For a standard sleep schedule built from parameters:

• opcode 01
• source id ff ff
• enabled bytes 00 01 00
• timestamp = selected sleep time
• type-specific block = 00 0e 01 01 00 02 01 01 03 02 4c 02 05 02
• fade = requested fade in deciseconds
• title field = 0x0118 + title_len
• type flag byte = 01
• recurrence/sentinel = ff ff ff ff
• final byte = 01

For a standard wake schedule built from parameters:

• opcode 01
• source id ff ff
• enabled bytes 00 01 00
• timestamp = visible wake time minus fade duration
• type-specific block = 00 0e 01 01 01 02 01 fe 03 02 bf 01 05 02
• fade = requested fade in deciseconds
• title field = 0x0118 + title_len
• type flag byte = 00
• recurrence/sentinel = ff ff ff ff
• final byte = 01

Create success notifications:

01 00 ff ff <new_id_le>
04 ff ff <new_id_le>

Create failure notification:

01 01 ff ff ff ff

Read Back One Schedule In Detail

Detail-read is a short request followed by a containerized schedule body.

Request format:

02 <schedule_id_le> 00 00

Response shape:

02 00 <schedule_id_le> <body_len> 00 00 00 <body...>

The <body...> bytes can be reconstructed into a normal schedule-like payload as:

01 <schedule_id_le> <body...>

That reconstructed payload reuses the same offsets as create/update payloads, which is why read-back decoding can extract title, kind, fade, timestamp, UUID, and enabled flag directly.

5. Update An Existing Schedule

Update reuses the full schedule-body format from create, but changes the source id and, when toggling state, the enabled bytes.

Generic update prefix:

01 <source_id_le> 00 <enabled_flag> 00

Rules:

• the full body must be resent, not just the changed field
• source_id_le is the existing schedule id to replace
• the final byte of the payload mirrors the enabled flag
• the bulb does not mutate schedules in place; it returns a replacement id

Update success notifications:

01 00 <source_id_le> <new_id_le>
04 <source_id_le> <new_id_le>

Activate Or Deactivate A Schedule

Activate and deactivate are specialized update operations using the same full-body update format.

Deactivate:

01 <source_id_le> 00 00 00 ... <final_byte=00>

Activate:

01 <source_id_le> 00 01 00 ... <final_byte=01>

Confirmed live deactivate example:

01 02 00 00 00 00 ...
01 00 02 00 03 00
04 02 00 03 00

Meaning: schedule id 2 was replaced by disabled schedule id 3.

Confirmed live reactivate example:

01 03 00 00 01 00 ...
01 00 03 00 04 00
04 03 00 04 00

Meaning: schedule id 3 was replaced by enabled schedule id 4.

Delete A Schedule

Delete is a separate short command and does not use the full schedule body.

Request format:

03 <schedule_id_le>

Success notifications:

03 00 <schedule_id_le>
04 <schedule_id_le> ff ff

Confirmed example for deleting schedule id 5:

03 05 00
03 00 05 00
04 05 00 ff ff

Missing pieces

I don't have access to repeating schedules or other options which are paywalled on the app.
The following parts are still partly inferred even though the overall command format is operational:

• the exact semantics of the fixed bytes at offsets 10..22 beyond their role as kind/behavior descriptors
• the deeper meaning of the 0x0118 + title_len field at offsets 25..26, even though it is confirmed for the standard wake/sleep builder
• whether the sentinel ff ff ff ff is strictly a recurrence mask, a default-all-days marker, or another scheduler bitfield
• whether additional app-side wake or sleep styles use different type-specific fixed blocks beyond the standard variants already captured