I run wlsunset as `wlsunset -S 6:00 -s 20:00 -d 3600 -t 2800`, I even 
tried changing it to `-S 4:00`, but no matter what I do, in the morning 
the colour temperature change persists until 10:00 and then changes to 
normal suddenly without any transition. Why could it be?

This could be a timezone issue. Can you try to input the time as UTC?

wlsunset operates entirely in UTC internally to normalize time against 
orbit calculations, but as a side-effect the manual time input is 
currently also UTC. It's a little annoying to fix in a portable way 
(i.e. works both on Linux and FreeBSD), so I haven't looked at it yet.

How to input the time as UTC? Is there some kind of format to input a 
timezone with the time?

On 02/05/2022 19.19, Kenny Levinsen wrote:
> This could be a timezone issue. Can you try to input the time as UTC?
>
> wlsunset operates entirely in UTC internally to normalize time against 
> orbit calculations, but as a side-effect the manual time input is 
> currently also UTC. It's a little annoying to fix in a portable way 
> (i.e. works both on Linux and FreeBSD), so I haven't looked at it yet.
>
>

Just specify what the time would be in UTC-land - if you want sunrise 
at 6AM your time, and you're in UTC+4, you say 2AM instead.

It's a little clumsy, but it'll take a bit before I have time to look 
at fixing the manual time input. Automatic calculation using 
latitude/longitude is the primary way to use wlsunset.

Nah, this doesn't work. At least sunset time is interpreted as a local 
time, that's for sure.

On 02/05/2022 22.04, Kenny Levinsen wrote:
> Just specify what the time would be in UTC-land - if you want sunrise 
> at 6AM your time, and you're in UTC+4, you say 2AM instead.
>
> It's a little clumsy, but it'll take a bit before I have time to look 
> at fixing the manual time input. Automatic calculation using 
> latitude/longitude is the primary way to use wlsunset.
>
>

I started wlsunset yesterday with desirable for me -S and -s option 
values (by local time). At the specified time of sunset it started 
gradually decreasing the colour temperature until the calculated time of 
dusk. But at the calculated time of dawn happened as well as at the 
specified time of sunrise. Only at 10:00 it suddenly reverted the colour 
temperature back to normal, without any gradual change. I must say that 
I live in UTC+10 timezone, so my local 10:00 is UTC 0:00.

On 02/05/2022 22.04, Kenny Levinsen wrote:
> Just specify what the time would be in UTC-land - if you want sunrise 
> at 6AM your time, and you're in UTC+4, you say 2AM instead.
>
> It's a little clumsy, but it'll take a bit before I have time to look 
> at fixing the manual time input. Automatic calculation using 
> latitude/longitude is the primary way to use wlsunset.
>
>