cocoa - How to create a specific date in the distant past, the BC era -

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i’m trying create date in bc era, failing pretty hard. following returns ‘4713’ year, instead of ‘-4712’:

  nscalendar *calendar = [[nscalendar alloc] initwithcalendaridentifier:nsgregoriancalendar];   nsdatecomponents *components = [nsdatecomponents new];   [components setyear: -4712];   nsdate *date = [calendar datefromcomponents:components];   nslog(@"%d", [[calendar components:nsyearcalendarunit fromdate: date] year]);

any idea i’m doing wrong?

update: working code

    nscalendar *calendar = [[nscalendar alloc] initwithcalendaridentifier:nsgregoriancalendar];     nsdatecomponents *components = [nsdatecomponents new];     [components setyear: -4712];     nsdate *date = [calendar datefromcomponents:components];     nsdatecomponents *newcomponents = [calendar components:nseracalendarunit|nsyearcalendarunit fromdate:date];     nslog(@"era: %d, year %d", [newcomponents era], [newcomponents year]);

this prints 0 era, ben explained.

your code working fine. since there’s no year zero, -4712 year 4713 bc. if check era component you’ll see it’s zero, in gregorian calendar indicates bc. flip negative sign , you’ll see 4712 ad (era 1).


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