It would also be possible to implement `json.Marshaler` to use a different time format. In particular, it might be reasonable to encode the zero value of time.Time as `null`, instead of a string (though mixed types in json messages are… icky).
Personally, I'm always very cautious about encoding and decoding times. There isn't really a standard way to transmit timezone information, especially as timezone definitions can even change over time, AIUI. So, even if you specify which timezone a point in time should be in, you can't rely on the receiver of the message having the same understanding of that timezone. Using UTC for storage and transmission is probably a better option. You essentially treat the stored data purely as "a point in time", while timezone info is specific to the presentation. A time.Time isn't just a point in time, though, so if you really marshal "a time.Time", you have to somehow include timezone info - so I kinda understand why the default MarshalJSON method doesn't convert it to UTC first. On Sat, Nov 28, 2020 at 10:35 AM Matt Harden <matt.har...@gmail.com> wrote: > > > On Fri, Nov 27, 2020 at 4:14 PM 'Robert Ma' via golang-nuts < > golang-nuts@googlegroups.com> wrote: > >> Is this because the 2-second offset of LMT gets lost in RFC 3339 >> representation? >> > > Yes, that's exactly it. > > >> On Fri, Nov 27, 2020 at 6:33 PM Robert Ma <rober...@google.com> wrote: >> >>> Hi all, >>> >>> Time is complicated. >>> >> > Wibbly-wobbly, even. > > Today I found myself in a rabbit hole. For some unrelated reason, I got a >>> time value in a non-UTC location that's otherwise zero (IsZero=true). This >>> value doesn't seem to survive a roundtrip to JSON. See this playground for >>> a minimal reproduction: https://play.golang.org/p/QdglfKYkstS >>> >>> Is this expected, a bug, or an undefined behaviour? I checked RFC 3339, >>> which time uses as the JSON serialization format, and it seems to support >>> 0000AD to 9999AD, but I have to admit I know little about time. >>> >> > RFC 3339 doesn't support sub-minute timezone offsets, so it's not possible > to format the LMT zone precisely. > > I am concerned that the time printed is incorrect by 2 seconds in this > case, and (I imagine) could be anywhere from 0 to 59 seconds off depending > on the particular sub-minute timezone offset used. That seems like a real > bug, and I don't know what a proper fix would look like. Perhaps when the > timezone is formatted in numeric form, the printed time should be adjusted > to account for the loss of precision in the zone info. In your case this > would print "0000-12-31T19:04:00-04:56" instead > of "0000-12-31T19:03:58-04:56". That solution has its own issues though. > > You probably should only use IsZero() to detect uninitialized time values; > never on a value that's been parsed from any source, even JSON. > > To get arbitrary time values to survive a JSON round trip, I think using > UTC exclusively would be the best option. > > >>> Cheers, >>> Robert >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "golang-nuts" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to golang-nuts+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/CAOPAaN%2BWvZ73Z-oMVaGmDt-Gr5DEk7ZtQeU43x5fKrCFW42%3DqQ%40mail.gmail.com >> <https://groups.google.com/d/msgid/golang-nuts/CAOPAaN%2BWvZ73Z-oMVaGmDt-Gr5DEk7ZtQeU43x5fKrCFW42%3DqQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/CALRNMm0VN8030%2BQLY0sLr%2BuHfz4WoG7NfWe1RUHj-d2Zqh393Q%40mail.gmail.com > <https://groups.google.com/d/msgid/golang-nuts/CALRNMm0VN8030%2BQLY0sLr%2BuHfz4WoG7NfWe1RUHj-d2Zqh393Q%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAEkBMfFx13J%3DiSx7y_hPKNFd8WPO9gVSUz9H_PKsNKjfgnNMPA%40mail.gmail.com.
