Although the various specs prefer [1] numeric timezones allowed by rfc822 [2] for the cookie expires field, some browsers discard cookies with dates in this format (latest chrome and safari at the time of writing). Firefox does seem to respect this aspect of the specs.
I don't currently have any other supporting evidence, except that @neilprosser I have tried this on Linux with Chrome, Chromium and Firefox, and on OSx with Safari, Chrome and Firefox.
Although the various specs prefer [1] numeric timezones allowed by rfc822 [2] for the cookie expires field, some browsers discard cookies with dates in this format (latest chrome and safari at the time of writing). Firefox does seem to respect this aspect of the specs.
I don't currently have any other supporting evidence, except that @neilprosser I have tried this on Linux with Chrome, Chromium and Firefox, and on OSx with Safari, Chrome and Firefox.
[1] https://tools.ietf.org/html/rfc1123#section-5.2.14 [2] https://tools.ietf.org/html/rfc822#section-5.1
Kudos to @neilprosser for spotting this!