Some key uses of the IOS oc-date date classes

NSDate is a class of dates Create a date

*date gets the time in whichever time zone it is, the time of the corresponding 0 time zone is printed 
nsdate *date =[nsdate Date];
NSLog (@ "%@", date);
Results: 2015-07-23 16:04:00.431 oc07_nsdate[1430:100568] 2015-07-23 08:04:00 +0000

get the current time zone

Nstimezone *zone =[nstimezone Systemtimezone];
NSLog (@ "%@", zone);
Result: 2015-07-23 16:03:27.180 oc07_nsdate[1422:100218] Asia/shanghai (gmt+8) offset 28800 Get the number of seconds that differ from the 0 time zone

Nsinteger seconds =[zone Secondsfromgmtfordate:date];
NSLog (@ "%ld", seconds);
Results: 2015-07-23 15:59:40.371 oc07_nsdate[1406:99223] 28800 through the difference of seconds, can get to the present time

NSDate *localdate =[nsdate datewithtimeintervalsincenow:seconds];
NSLog (@ "%@", localdate);

nstimeinterval: Time interval

Nstimeinterval: Corresponding to the double type
Nstimeinterval calculates the time interval for two time objects

Nstimeinterval interval =[tomorrowdate timeintervalsincedate:date];
NSLog (@ "%g", interval);
Results: 2015-07-23 16:21:11.947 oc07_nsdate[1489:104070] 115200

Example 1

Calculate the current time and ⼀ a fixed time difference, if the difference in 60 seconds, output "just", if in 60 seconds outside 3,600 seconds, output "xx minutes ago," if 3,600 seconds, 3600*24 seconds, output "Xx⼩ hours ago."
    nsdate *date1=[nsdate datewithtimeintervalsincenow:1000];
Nstimeinterval time =[date1 timeintervalsincedate:date];
NSLog (@ "%ld", (Nsinteger) time);
if (time <60) {
    NSLog (@ "just");
} else if (time >=60) && (Time <3600) {
    NSLog (before%ld minutes), (Nsinteger) time/60);
else if (time >= 3600) && (time<3600*24)) {
    NSLog (@ "%g hours ago", time/3600);
}

convert dates and strings to each other

NSDate-> nsstring
    nsdate *date Date];
NSString *datestr =[nsstring stringwithformat:@ "%@", date];
NSLog (@ "%@", datestr);
Results: 2015-07-23 17:13:16.597 oc07_nsdate[1730:117413] 2015-07-23 09:13:16 +0000

String-> nsdate
And cut the time back 8 hours.

NSString *timestr =@ "2015-7-23 17-18-10";
NSDate *date=[formatter Datefromstring:timestr];
NSLog (@ "%@", date);

The format of the time
YYYY-MM-DD Hh-mm-ss
H 24-hour system, H 12-hour system first set the time format, to convert the time and format to match

NSDateFormatter *formatter =[[nsdateformatter alloc] init];
[Formatter setdateformat:@ "Yyyy-mm-dd Hh-mm-ss"];
NSDate *date=[nsdate Date];
Through the format, the specified time is directly converted to NSString in
 this way, the system will also switch time to the present time
nsstring *strdate =[formatter stringfromdate:date];
NSLog (@ "%@", strdate);
 Results: 2015-07-23 17:16:11.551 oc07_nsdate[1747:118395] 2015-07-23 17-16-11