Duty Setup improvements
It will be possible to set up the duty timeframes based on the standard time brackets as well as on Sunset and Sunrise.
Duty Setup section

Updated 'Default times' subsection
The 'Default times' subsection will be updated with the 'Sunset/Sunrise dependent' settings.
The setup and calculations will work as follows:
All day - if this checkbox is ticked, the rest of the options within the 'Default times' subsection remain inactive. Unticking it will activate the remaining fields
Sunset/Sunrise dependent - option to activate the calculations based on Sunset and Sunrise
Sunrise offset - number of minutes against the time of the sunrise. Can be inserted as a positive (30), negative (-30), empty, or zero value. Positive value will indicate the timeframe after the sunset/sunrise, and the negative value will indicate the timeframe before the sunset and sunrise
Sunset offset - number of minutes against the time of the sunset. Values are adequate to the ones explained above
From - fixed time for the start of the duty
To - fixed time for the end of the duty
Timeframe conditions
The following conditions will apply to the duty times calculations:
Example

Adding duty with sunset and sunrise setting activated
As per the screenshot on the right-hand side, adding the duty with the 'Sunset/Sunrise dependent' option activated blocks the possibility of changing the timeframes.
The duty is added on the 1st of March for EPWA airport with the sunrise at 06:21LT and the sunset at 17:17LT.
The duty definition from the screenshot has the following timeframe settings:
Sunset/Sunrise dependent - activated
Sunrise offset - set to '30' which indicates 30 minutes after the sunrise, ie 06:21LT + 00:30 = 06:51LT
Sunset offset - set to '-30' which indicates 30 minutes before the sunset, ie 17:17LT - 00:30 = 16:47LT
From - set to 06:00 in UTC
To - set to 20:00 in UTC
Based on the conditions, the duty times, including the duty times for FTL calculations purposes, are set as per below:
Duty start - 06:00UTC, because fixed 06:00UTC (07:00LT) is later than the sunrise time plus the sunrise offset of 06:51LT
Duty end - 15:47UTC, because the sunset minus the sunset offset of 15:47UTC (16:47LT) is earlier than fixed 20:00UTC (21:00LT)