Hello, First of all, I would like to thank you for all the works accomplished by your teams !!
I'm currently implementing functions in bash which are using the command "date". I have noticed something strange when I realize manipulation during the daylight saving from Winter to Summer times in Europe. Let me know, if it's the good place to submit my question or where I could do it. In France, this year (2024), we have changed time during the night between the 30th and 31st of March. At 2.00 AM (31st march) -- it was --> 3.00 AM (31st march) So if I do the date operation 30th march 2.30AM + 1 day, I'm expecting something like 31st march 3.30AM. Observation using containers: bash - date (GNU coreutils) 9.5 $ docker run --rm -it docker.io/bash:5.2.32 $ apk update $ apk add --no-cache coreutils tzdata $ date --version date (GNU coreutils) 9.5 $ export TZ="Europe/Paris" $ date -d "2024-03-30T02:30:00.123+0100 + 1 days" "+%FT%T.%3N%z" 2024-03-31T01:30:00.123+0100 $ date -d "2024-03-30T02:30:00.123+0100 + 24 hours" "+%FT%T.%3N%z" 2024-03-31T03:30:00.123+0200 # Minus looks fine $ date -d "2024-03-31T03:30:00.123+0200 - 1 days" "+%FT%T.%3N%z" 2024-03-30T02:30:00.123+0100 $ date -d "2024-03-31T03:30:00.123+0200 - 24 hours" "+%FT%T.%3N%z" 2024-03-30T02:30:00.123+0100 The logic behind this is that the 31st is a day with 23 hours only, so 1 day was considered as 23 hours even if we didn't include all this day. $ date -d "2024-03-30T02:30:00.123+0100 + 23 hours" "+%FT%T.%3N%z" 2024-03-31T01:30:00.123+0100 This behavior could be understood when we are taking a more simple case (that's the current result): 2024-03-30T13:30:00.123+0100 + 1 day => 2024-03-30T14:30:00.123+0200 But I understand less when we fall in the time shift window. Question 1: Should 3.30AM be the good result to the operation "2024-03-30T02:30:00.123+0100 + 1 days" ? In addition, I have tested on other virtual environments (sorry I don't have a native one :( ) and results are again differents. OS | Core Utils | +1 day | +24 hours | docker.io/bash:5.2.26-alpine3.19 | 9.4 | 2024-03-31T01:30:00.123+0000 | 2024-03-31T03:30:00.123+0200 | VM Ubuntu 24.04 | 9.4 | 2024-03-31T04:30:00.123+0200 | 2024-03-31T03:30:00.123+0200 | Debian 12.7 | 9.1 | 2024-03-31T04:30:00.123+0200 | 2024-03-31T03:30:00.123+0200 | Git Bash | 8.32 | 2024-03-31T01:30:00.123+0000 | 2024-03-31T01:30:00.123+0000 | Question 2: Is there something else than Core Utils which could have an effect on what the command date returns ? The Winter daylight saving looks fine: $ date -d "2023-10-28T03:30:00.123+0200 +1 days" "+%FT%T.%3N%z" 2023-10-29T02:30:00.123+0100 $ date -d "2023-10-28T03:30:00.123+0200 +24 hours" "+%FT%T.%3N%z" 2023-10-29T02:30:00.123+0100 $ date -d "2023-10-29T03:30:00.123+0100 -1 days" "+%FT%T.%3N%z" 2023-10-28T04:30:00.123+0200 $ date -d "2023-10-29T03:30:00.123+0100 -24 hours" "+%FT%T.%3N%z" 2023-10-28T04:30:00.123+0200 May, I misleading and I did'nt used the good format or others, let me know if it's the case. Thanks in advance for your feedbacks. Best Regards. ________________________________________________________________ Benjamin VARGIN
