UIDatePicker minimumdate

Question

I'm confused with one question. I don't understand where I made mistake

I needed make minimumdate for my UIDatePicker near 1810 year. So I try make it like

    datePicker.minimumDate = [[NSDate alloc] initWithTimeIntervalSince1970: - (60 * 60 * 24 * 365 * 160)];

But I get wrong minimumdate:

So I went the other way and solved the problem

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *comps = [NSDateComponents new];
comps.year = -160;
datePicker.minimumDate = [calendar dateByAddingComponents:comps toDate:[NSDate dateWithTimeIntervalSince1970:0] options:0];

But I can'nt understand why in the first case I get wrong minimumdate

Answer 1

datePicker.minimumDate = [[NSDate alloc] initWithTimeIntervalSince1970: - (60 * 60 * 24 * 365 * 160)];

160 Years are not 60 sec * 60 min * 24 hours * 365 days.

You did not take consideration of various factors, one of the easiest to know is leap year.

Edit:

Use 60.0 * 60 * 24 * 365 * 160 to make one of then float, so the result will be float as you may exceed the int32(ios) range.