Calendars & Calendar Conversions

[josevalim]

@Qqwy

When talking to @kip about this yesterday, he came with the very astute observation that it might very well be simplified to ‘just’ using a float: {integer_days, float_last_day_fraction}. While floats have a rounding error, the 16 decimals of guaranteed matissa precision are enough to work with times in sub-microsecond format.

Ok, that was going to be my follow up point. It seems when encoding times between different calendars we would lose precision anyway because the days are slightly longer or shorter. So the “leap seconds base” is only useful when encoding in the same calendar. But, if it is the same calendar, we don’t need to encode the time.

@Qqwy

Only if the to-be-encoded datetime is in UTC, i.e. Calendar.ISOor erlang-time-tuple format.
And then only if the to-be-encoded datetime is June 30th or December 31th.

Perfect. This clarifies it. So would it make sense to rather add two functions to the Calendar behaviour? One that converts a Date to integer and another that converts the Time to a fraction? There is no need to convert the time if you are interested only on the date. /cc @kip