Adding fixed amount of time to a calendar start time

I want to add/subtract a fixed amount of time to the time returned by this function:

$df(hh:mm, ci(start, 0, a1d))$ 

The function returns the start time of the first calendar event tomorrow. Let's say 09:40.

But I want to subtract 1 hour from that so that 08:40 is displayed.

Thanks in advance!

All dates in Kustom are translated in seconds behind the scenes, so you can just do $df(hh:mm, ci(start, 0, a1d) - 3600)$ to remove "3600" seconds to the result before printing it with df, so it will display the time one hour before.

OK, then I think I found a bug:

$df(hh:mm, ci(start, 0, a1d) - 3600)$

This seems to work fine as long as Location and TimeZone field is in "Default"

However, if the text item is in a layer that has Location set to anything other than "Default", then it does not work anymore.

For example: My Text field is in a layer set to London as location. The return value is 09:40.

When I subtract 3600 seconds (as above) it DOES NOT display 08:40, but 16:40 (which is my current time zone (device location) - 1hr).

Its almost as if subtracting the seconds overrides the location setting and changes it to Default.

The behaviour is the same for Location and TimeZone not being in Default.