Safari's Autofill feature may be distoring time

Repeated reports about inaccurate form filling have lingered for years

The autofill feature of Apple's Safari browser appears to be suffering from a date handling error that occasionally leads it to supply an incorrect credit card expiration date when filling out forms.

The supposed issue has been a sore spot for Apple customers dating back at least to 2017, when the author of an Apple Community forum post complained about changes to the month field in the Autofill credit card expiration date when moving between time zones.

"I've noticed for the last year or so, whenever I travel from Eastern time zone (my home) to Central time zone or even Pacific time zone that my credit card expiration date month changes in Safari Autofill," the Safari user wrote.

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Another post in 2021 raised similar concerns.

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"I don't know how to reproduce this," the author wrote. "Every few months Safari on any of my devices changes the expiration month of all of my stored credit cards by decreasing the month by 1, for example instead of 10/2029 it changes it to 09/2029."

Three years later, another person posting to Apple's Community forum reported the same issue.

"For a few years now every time I use Autofill on my computer my credit cards (ALL of them) always have their expiration dates change one month earlier," the 2024 post says. "I thought it was just a glitch on my computer but I bought a new computer and didn't transfer anything from my old one and it is still doing it."

An unrelated Autofill bug report from 2024 suggests that if there is an issue, it resides in Apple-owned Safari code rather than Safari's open source WebKit engine.

Wherever the bug may reside, Safari's unreliable handling of credit card dates has kept a complaint-filled Reddit thread going for four years. And the reported month-shifting has been noted in other threads, too.

The Register was unable to reproduce the described behavior, but a reader insists it's still a problem.

"The Safari AutoFill feature sometimes fills in the credit card expiration date wrong," the reader explained. "My credit card expires in December, but sometimes Apple helpfully enters November."

"To be clear, the card is stored correctly when inspected in Settings," our tipster added. "The off-by-one error only happens when filling out a form in Safari, and not consistently."

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One possible way this might happen is if the Safari Autofill code implemented the expiration date using Swift's DateComponent type and stored it as a Calendar object with UTC as the TimeZone identifier. Doing so would anchor the date to a specific time. If the date components were extracted in Pacific Time, the value would be represented as eight hours ahead (PST). So 9/1/2027 at 00:00 would appear as 8/31/2027 at 16:00.

Apple did not immediately respond to a request for comment, but we're told Apple's Help Desk – or "Helpless Desk" as our source put it – advised clearing the browser cache and re-entering details of the affected credit card. 

If that works, it suggests Safari's handling of cached data in the context of Autofill dates may need to be revisited.

Apple does not maintain a public bug database and the community-maintained OpenRadar sheds no light on these reports. ®