Six formats for one date

A small engineering war story. Indian invoices write dates in at least six common formats, and two of them are ambiguous with each other. 07/03/2025 is March 7 or July 3 depending on the billing software, and both interpretations are plausible for a purchase date.

Getting this wrong is not cosmetic. A swapped day and month can move a warranty expiry by four months, which means we either tell a user their coverage is over while it is active, or worse, promise coverage that already lapsed.

Our resolution stack, in order: explicit format cues elsewhere on the invoice, GST filing conventions of the retailer, delivery or payment timestamps when the receipt came from email, and finally a confidence flag that asks the user to confirm instead of guessing silently.

The general principle: when a wrong answer is costly, an honest "please confirm" beats a confident guess. Applies to a lot more than dates.