Excel geht fälschlicherweise davon aus, dass das Jahr 1900 ein Schaltjahr ist | „Obwohl es technisch möglich ist, dieses Verhalten zu korrigieren, überwiegen die Nachteile die Vorteile.“
https://learn.microsoft.com/en-us/troubleshoot/microsoft-365-apps/excel/wrongly-assumes-1900-is-leap-year
25 Kommentare
Well I finally learned something in Reddit. I also thought 1900 was leap, but it is not. The OP is correct.
For anyone wondering, years divisible by 100 must also be divisible by 400 to be a leap year. It’s to make up for the bit of calendar drift that regular leap years dont.
Someone did not excel in math it looks like
How can this happen… like it’s not obviously.. to fix it would break something? What … lol 😂 it’s comical
Excel cannot compute dates before 01/01/1900 correctly
So every weekday before that is incorrect because of the extra day?
To be clear, this isn’t a bug in Excel; it was designed to do that.
It *was* a bug in Lotus 1-2-3, which was the second major spreadsheet program (after Apple’s VisiCalc and before Excel). Excel intentionally reproduced that behavior so it would be easier for businesses to switch from Lotus to Excel.
This is fairly well-known tech lore, but it’s also explained in the article.
They were too lazy to code a special case
This buries the lede: this error wasn’t made by the Excel team, it was made by the Lotus team & deliberately preserved when creating OG Excel for migration compatibility.
Way more stuff in our world is held together with duct tape & bubblegum than most people realize.
yup.
welcome to microsoft.
Its code is FULL of well known bugs that CANNOT be fixed, *because too much code has been written to work around them*.
UPDATED: added explanation in italics.
>the disadvantages of doing so outweigh the advantages
Until we get to 2100 and everything breaks
People have pointed out why this is (Lotus 1-2-3 compatibility), but it’s also good/fun to remember that datetime in computing is just….difficult. Not because of the concept, but because there are so many quirks in our datetime system that just build up. We have leap days, leap seconds, calendar changes, daylight saving time, timezones etc And lots of them have occurred a bit randomly over the years so whoever programs in your datetime conversions needs to take into account all the changes over the years.
People have written out the exact reasons in the comments but I need to come in with the [obligatory Tom Scott](https://youtu.be/bC6tngl0PTI?t=326&si=VLXxiuLf4oXwD0a0).
Lots of schoolyard defences going on in this article.
“He did it first, miss!”
“An older boy made me to do it”
MS ought to done it right a put the onus on them others.
Honestly, you shall not mess with excel. This is the cornerstone of the global financial system.
In the 5th grade I told my class that Feb 29, 2000 happens once every 400 years and everyone laughed at me, and the teacher said I was wrong and I tried to explain but no one listened. Smh
An early blogger, Joel Spolsky, wrote about this exact issue in his blog [My First BillG Review](https://www.joelonsoftware.com/2006/06/16/my-first-billg-review/). In it he described when he wrote the Excel Basic spec, he stumbled upon this error, and then went to an old Excel developer who enlightened him to the Lotus 123 issue. Finally, when Bill Gates interrogated him about his spec, he was able to respond to Bill’s hardest question with this arcane tidbit.
„It’s cheaper and easier to just do things wrong.“ FTFY
Some AI is going to try and fix this and it will end Excel.
Well it is under the Julian Calendar
but has Microsoft considered how funny it would be if they made a technically correct change that pissed off their entire user base by shifting every date by 1 day?
Nearly infinite backwards compatibility has its drawbacks
Of course it stems from Lotus Notes. God, that was such a dumpster fire program.
So glad I don’t have to support that crap at work anymore… <shudder>
Fun fact: There are a number if popular systems out there including classic Macs, Igor and Labview that use a Jan 1, 1904 epoch specifically because they didn’t feel like dealing with the 100 year leap year rule.