Scheduler skips first and last slots on single-day schedules

[lucamotta-canavisia]

Checklist

• I checked for similar existing issues (both open and closed) before posting.
• I will participate in further discussion about this issue and can help by testing (if requested).

Card Version

v4.0.11

Component Version

v3.3.8

Bug description

When creating a schedule for a single day (start = end), selecting multiple slots causes the first and last slots to appear empty, and the penultimate slot is never executed.

Steps to reproduce

1. Create a schedule for a single day (start = end).
2. Select multiple time slots throughout the day.
3. Assign a simple action to each slot (e.g., change thermostat setpoint and set mode to “heat”).
4. Ensure the first and last slots are empty

Additional info

Observed Behavior:

• The first slot shows no actions.
• The last slot shows no actions.
• The penultimate slot is never executed.

Note: If the last slot is explicitly filled with an action (e.g., a different thermostat setpoint), all slots execute correctly.

[nielsfaber]

In an attempt to reproduce the issue you are reporting, I made a single day (tomorrow, 24/02) schedule with only the first timeslot assigned:

Result:

In summary, a schedule with only first timeslot assigned seems to work fine for me.
I tried the same with more assigned timeslots, no problems found.

When creating a schedule for a single day (start = end), selecting multiple slots causes the first and last slots to appear empty,

I don't observe any such behaviour.
What you mean by 'appear empty'? is it a visual thing, or the action that is configured is not executed?

Your report also contains inconsistencies / confusing statements.
In Steps to reproduce you state

Ensure the first and last slots are empty

Later you state

Observed Behavior:
The first slot shows no actions.
The last slot shows no actions.

Which is in line with how you configured it yourself?

Please share a screen video to illustrate your issue. Or any other proof that supports this bug report.

[lucamotta-canavisia]

Sorry, maybe it wasn't clear enough. Here is a schedule that doesn't work:

• the first and last slots are empty (i.e. no action)
• middle slots sets target temperature/hvac mode for the same climate entity to two different temperatures (19 and 21 degrees)
• first non empty slot is executed (climate is set to heat/19 degrees)
• second non empty slot is no executed (climate stays to heat state/19 degrees instead of 21 degrees)

Looking at the history of the climate i can see there is no action, even though the schedule is marked as "on". If however I set an action for the last empty slots (say, climate off), the 21 degrees slot is executed as expected.

Hope this clarifies

[lucamotta-canavisia]

I did another test and it seems I can reproduce it now:

• create the schedule for a day in the future (e.g. from 27/02/2026 to 27/02/2026 created today, 26/02)
• add three slots (doesn't matter which time) and actions (mine are "hvac set off" for the first slot, "hvac set temperature setpoint" for the next two with 19 and 20 degrees)
• nothing will happen the next day

If i do the same thing for the same day (i.e. from 26/02 to 26/02 created on 26/02) the schedule works: as soon as it is saved, a timer is set for the next event border.

The next day the schedule won't trigger. Looking at the activity logs you'll see a "entity turned on" log at 00:00/00:01 but no action is executed.
I enabled debug logs for the scheduler components and I can see no logs near the border of two slots (i.e. nothing executed) so I suspect the problem is related to the fact that the switch associated with the schedule is off until midnight of the day of execution.
There are a few more notes that can be of help:

• although the scheduler is updated to its latest version, it's running on home assistant 2025.11.3
• home assistant is installed on a raspberry pi (old version, hence the problem with 2025.11.3 not being updated because of 32/64 bit problem). Might it be that a slow system could influence the switch turn on system?

[nielsfaber]

I created the following scheme:

I configured it to execute tomorrow 28/02 only:

I made sure garden lights are off (and remain off today):

After saving, the schedule is planned for 00:00:

I can also see this from the logs of the scheduler-component:

2026-02-27 07:00:22.364 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 669679 set for 2026-02-28 00:00:00+01:00

I'm fairly sure that tomorrow at 00:00 the garden lights will be switched on.
But I will let you know.

Note that this will be my last attempt of trying to reproduce the issue. Please let me know if I set up the schedule wrongly, I understood from the info you gave me that the configuration above is sufficient to observe the claimed bug.

[lucamotta-canavisia]

So I finally have some debug log for this bug. I tried this:

• two schedules, as per screenshots (one with an empty/null slot at the start, id #807b27, the other, id #61d83f, with several slots filled with the same action, set hvac temperature, with different setpoint or off). both of them are set "from 27/02 to 27/02".

• one schedule that runs every day (id #14b1b2)

• this is the debug log of the activities:

2026-02-26 17:01:31.558 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 14b1b2 set for 2026-02-26 21:00:00+01:00
2026-02-26 17:01:32.599 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 14b1b2 set for 2026-02-26 21:00:00+01:00
[...]
2026-02-26 17:04:45.520 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 61d83f set for 2026-02-27 00:00:00+01:00
2026-02-26 17:20:26.278 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 807b27 set for 2026-02-27 03:00:00+01:00
[...]
2026-02-26 21:00:00.002 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 14b1b2 has reached slot 2
2026-02-26 21:00:00.003 DEBUG (MainThread) [custom_components.scheduler.switch] Schedule 14b1b2 is triggered, proceed with actions
2026-02-26 21:00:00.004 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Executing action climate.set_hvac_mode on entity climate.termostato_locale_128
2026-02-26 21:00:00.038 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Finished execution of tasks
2026-02-26 21:01:00.058 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 14b1b2 set for 2026-02-26 23:59:59+01:00
[...]
2026-02-26 23:59:59.237 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 14b1b2 has reached end of timeslot, resetting..
2026-02-26 23:59:59.238 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 14b1b2 set for 2026-02-27 00:00:00+01:00
[...]
2026-02-27 00:00:00.755 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 61d83f has reached slot 0
2026-02-27 00:00:00.763 DEBUG (MainThread) [custom_components.scheduler.switch] Schedule 61d83f is triggered, proceed with actions
2026-02-27 00:00:00.763 DEBUG (MainThread) [custom_components.scheduler.actions] [61d83f]: Executing action climate.set_hvac_mode on entity climate.termostato_locale_128
2026-02-27 00:00:00.763 DEBUG (MainThread) [custom_components.scheduler.actions] [61d83f]: Action has no effect, skipping
2026-02-27 00:00:00.768 DEBUG (MainThread) [custom_components.scheduler.actions] [61d83f]: Finished execution of tasks
[...]
2026-02-27 00:00:01.753 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 14b1b2 has reached slot 0
2026-02-27 00:00:01.753 DEBUG (MainThread) [custom_components.scheduler.switch] Schedule 14b1b2 is triggered, proceed with actions
2026-02-27 00:00:01.753 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Executing action climate.set_hvac_mode on entity climate.termostato_locale_128
2026-02-27 00:00:01.754 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Action has no effect, skipping
2026-02-27 00:00:01.754 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Finished execution of tasks
2026-02-27 00:01:01.764 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 14b1b2 set for 2026-02-27 05:30:00+01:00
2026-02-27 00:01:00.775 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 61d83f set for 2026-02-27 02:30:00+01:00
[...]
2026-02-27 02:30:00.001 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 61d83f has reached end of timeslot, resetting..
2026-02-27 02:30:00.012 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 61d83f set for 2026-02-27 04:00:00+01:00

[...]
2026-02-27 03:00:00.001 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 807b27 has reached slot 0
2026-02-27 03:00:00.012 DEBUG (MainThread) [custom_components.scheduler.switch] Schedule 807b27 is triggered, proceed with actions
2026-02-27 03:00:00.014 DEBUG (MainThread) [custom_components.scheduler.actions] [807b27]: Executing action climate.set_hvac_mode on entity climate.termostato_locale_128
2026-02-27 03:00:00.041 DEBUG (MainThread) [custom_components.scheduler.actions] [807b27]: Entity climate.termostato_locale_128 is already set to heat, proceed with next task
2026-02-27 03:00:00.041 DEBUG (MainThread) [custom_components.scheduler.actions] [807b27]: Executing action climate.set_temperature on entity climate.termostato_locale_128
2026-02-27 03:00:00.062 DEBUG (MainThread) [custom_components.scheduler.actions] [807b27]: Finished execution of tasks
2026-02-27 03:01:00.069 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 807b27 set for 2026-02-27 09:00:00+01:00
2026-02-27 04:00:00.002 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 61d83f has reached end of timeslot, resetting..
2026-02-27 04:00:00.016 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 61d83f set for 2026-02-27 05:00:00+01:00
[...]
2026-02-27 05:00:00.003 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 61d83f has reached end of timeslot, resetting..
2026-02-27 05:00:00.021 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 61d83f set for 2026-02-27 11:00:00+01:00
[...]
2026-02-27 05:30:00.142 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 14b1b2 has reached slot 1
2026-02-27 05:30:00.142 DEBUG (MainThread) [custom_components.scheduler.switch] Schedule 14b1b2 is triggered, proceed with actions
2026-02-27 05:30:00.144 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Executing action climate.set_hvac_mode on entity climate.termostato_locale_128
2026-02-27 05:30:00.144 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Action has no effect, skipping
2026-02-27 05:30:00.144 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Executing action climate.set_temperature on entity climate.termostato_locale_128
2026-02-27 05:30:00.161 DEBUG (MainThread) [custom_components.scheduler.actions] [14b1b2]: Finished execution of tasks
2026-02-27 05:31:00.172 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 14b1b2 set for 2026-02-27 21:00:00+01:00
[...]
2026-02-27 09:00:00.001 DEBUG (MainThread) [custom_components.scheduler.timer] Timer 807b27 has reached end of timeslot, resetting..
2026-02-27 09:00:00.012 DEBUG (MainThread) [custom_components.scheduler.timer] Timer of 807b27 set for 2026-02-27 23:59:59+01:00

• the activity logs of the climate entity. The climate entity switched to "heat" at 3am, but the schedule #61d83f should have set it to heat at 2:30am

As you can see from the logs:

• Schedule #61d83f executed at midnight (no action, climate was already off) but at 2:30, 4:00 and 5:00am it fired but without executing associated actions (setting hvac to heat and to some setpoint)
• Schedule #807b27 executed the action at 3 am but then at 9am did nothing (i.e. it didn't update the setpoint)
• #14b1b2 executed its actions with no problems

[nielsfaber]

I can confirm something is wrong.
The schedule I set up for testing didn't execute the middle timeslot.
The problem seems only to occur in case of setting a date period (or specific day only).
Unfortunately this seems to be related to code that hasn't been touched in years.
At this point I have no idea what causes it and how to fix it.