How to best debug NSDate / NSTimezone related code

Question

I know that NSDate does not represent a timezone, but perhaps someone can advise me on how to best debug its relationship to other classes, for example NSDatePicker, CalCalendarStore.

As an example, I want to set the date for a date picker to 01-01-2012. I do something like this:

newDate = [NSDate date];
NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar];
NSDateComponents *components = [calendar components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:newDate];
[components setMonth:1];
[components setDay:1];
newDate = [calendar dateFromComponents:components];

This works fine in my datepicker, but as soon as I try debugging date-related code, things get very confusing (with TZ-related shifts in the hour, sometimes even day). Can someone advise me on how to do this?

If I should use a date formatter (probably!), how should I do this so I can easily debug without cluttering up the code too much?

Answer 1

NSDate is just a wrapper around unix time and as such is not time zone aware at all, its actually your date formatter that puts a time zone of any kind on it.

Dealing with similar problems I ended up just forcing all my NSDate objects to use UTC dates (when not worrying about the "time" components themselves).

You have to use a new NSCalendar instance with the timezone property set to UTC to make those dates, but this way you're dealing with consistant dates, just use a UTC time zone set formatter to display them, or a UTC set Calendar to break them up into components as needed.