[email protected] schrieb am Samstag, 26. April 2025 um 13:01:58 UTC+2:

I still don't get it. A system that isn't DST aware, shouldn't produce DST 
related differences. If it does, it fails to make sure, that it strips any 
DST related offsets for values that may be passed, before doing it's 
calculations.


You may want to read about Python's datetime module. 

As I said before, time can be a scalar value of seconds or a tuple 
containing year, month, day, hour, minute, and second. WeeWX converts 
between them. If you want to understand timespans you have to understand 
when exactly which of those two is used and when conversion takes place. 

$span uses weeutil.weeutil.archiveSpanSpan to get the timespan. It receives 
a timestamp as a scalar value (seconds since 1970-01-01 00:00:00 UTC). 
First it converts that timestamp to a tuple in *local* time. Then it 
applies the deltas except the month delta using Python's datetime.timedelta 
class. See the Python documentation how it works in particular. For the 
month delta the method contains a special calculation. After all that 
calculating the tuple is converted back to a scalar value in seconds. The 
final timespan contains of both those scalar values in seconds since 
1970-01-01 00:00:00 UTC. The length of the timespan is simply the 
difference of those values. It is the real amount of seconds. And this 
amount of seconds is really 3600 seconds less or more if a daylight savings 
time switch is within the timespan. To print the value the seconds are 
converted to hours, minutes, and seconds.

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