I agree and my 2 cents: I can expect something different depending on the timezone and DST if I add years months weeks days hours minutes seconds to a given datetime Even though, in 90% of the cases, there is a more or less obvious conversion formula between all of them. But consider months to days. That is not clear at all. On 27.07.2015 19:11, Chris Angelico wrote: > On Tue, Jul 28, 2015 at 12:57 AM, Ronald Oussoren > <ronaldoussoren at mac.com> wrote: >> IMHO “+ 1 days” and “+ 24 hours” are two different things. Date >> arithmetic is full of messy things like that. “+ 1 month” is another >> example of that (which the datetime module punts completely >> and can be a source of endless bikeshidding). > https://www.youtube.com/watch?v=ppfpa5XgZHI > > MATLAB defines "+ 1 month" as, if I'm not mistaken, "add the time it > would take to go from the beginning of time to the beginning of > January of the year 0 (which is totally a thing, by the way)". I'm > fairly sure that this is the most WAT-worthy definition possible, as > it means that adding one month does nothing, and adding two months > adds the length of January (31 days)... and adding three months adds > January + February, *in a leap year*. > > But I agree that adding days and adding hours are different things. If > I add one day, I expect that the time portion should not change, in > the given timezone. (With the exception that DST switches might mean > that that time doesn't exist.) If I add 86400 seconds, I expect that > it should add 86400 ISO seconds to the time period, which might not be > the same thing. If you convert a datetime to a different timezone, add > 86400 seconds, and convert back to the original timezone, I would > expect the result to be the same as adding 86400 seconds to the > original, unless there's something seriously bizarre going on with the > size of the second. But if you convert, add 1 day, and convert back, > you will get a different result if the two differ on DST. Does that > sound plausible? > > ChrisA > _______________________________________________ > Python-Dev mailing list > Python-Dev at python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/srkunze%40mail.de
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4