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.netdatetimeoffset

(.net) Unexpected offest when call DateTime.Today.AddDays

I have a test that started to fail today, after a little investigation I found that the returned date differ by 1 hour, more precisely it results to have 1 hour offset (the current offset I have in my location now [correction: today offset is still 00:00]).
The test was fine yesterday. The same operation returned a date without that extra offset.

Today is 26 March 2022.
Tonight the offset time change in my location, At midnight we move the time 1 hour forward. ([correction] the change is done at 02:00 moving time to 03:00)
The date that result wrong is the date obtained by DateTime.Today.AddDays(2).
Note that if you add 1 day it seems ok.

let today = DateTime.Today
let tomorrow = DateTime.Today.AddDays(1.)
let nextDay = DateTime.Today.AddDays(2.)

Console.WriteLine($"today:    {today:o} {today.Kind}")
Console.WriteLine($"tomorrow: {tomorrow:o} {tomorrow.Kind}")
Console.WriteLine($"nextDay:  {nextDay:o} {nextDay.Kind}")

Output:
enter image description here

The nextDay date seems wrong to me. Why its offset is 01:00 ?
Because it is adding 48 hours and because of the time-change it also shows the "new" local offset?.
So, why it does not happen when I add 2 day ?
27 March (tomorrow) is already with 1 hour offset.
I'm missing something or that date is wrong as I think?

Solution

  • 27 March (tomorrow) is already with 1 hour offset.

    Not exactly. In most of Europe (including the UK, which seems to be your current location) daylight savings time starts at 27 March 01:00 UTC. At 27 March 00:00, you still have "winter time" in the UK with offset +00:00.