mm-dd-yy, dd-mm-yy or yyyy-mm-dd?

Vitalik Buterin says duh, go for the third option.

In fact, he says there is no such thing as the third option, yyyy-mm-dd is the only way to go about it.

My first job was with a firm called Genpact, and I was working for American clients, while being based out of Bangalore. mm-dd or dd-mm is a real problem, believe me.

Now, as an Indian, I’m tempted to say that dd-mm-yy is the “correct” way to go about it. Partially out of habit, as I’ve been writing dates in this format for all my life, but Vitalik Buterin does not approve:

But I’ve also argued in the past that writing the date in dd-mm-yyyy format makes sense because of an implicit order and logic in this way of writing it. The component that changes the most frequently (the day) comes first, the one that changes the second most frequently (the month) comes second, and the one that literally changes once a year comes third.

And if only the Americans hadn’t decided to go down the mm-dd-yyyy (why, America, why?), we could all have agreed upon this, and lived happily ever after.

But after much sighing and gnashing of teeth, I find myself – reluctantly – in Camp Buterin. yyyy-mm-dd is the only correct way to do it, as it removes any chance of ambiguity. dd-mm-yyyy is, I still hold, more logical, but yyyy-mm-dd has the least chance of confusion.

And this stuff matters, because dates can get really tricky when it comes to software. For exanple, did you know that dates in Excel are off by one day?

4 thoughts on “mm-dd-yy, dd-mm-yy or yyyy-mm-dd?”

1. Actually, I think that even if America hadn’t gone down the mm-dd route, yyyy-mm-dd would still have been the correct standard. The more salient point really is that general-purpose alphanumeric ascending order sort would also sort dates written in yyyy-mm-dd in ascending order. I name files like this in particular while writing code for this reason.

(Another perspective: while writing a number, the most significant digit is on the left: the digit which when changed would change the value of the number the most. This property is also preserved while writing time hour:min. Makes sense to also have the year first in dates, to preserve this property.)

• Ah, this was a lightbulb moment for me. Thank you! π

2. Ashwath says:

Looks interesting, but the “Indian” in me will continue with the dd-mm-yyyy format forever I guess haha.

• I know the feeling, trust me π