Convert a NSDate to milliseconds epoch time

问题:

I need to be able to convert a date to a time stamp, an epoch in milliseconds. All I see online are for converting milliseconds to NSDate and not the other way round. Any help out there?

回答1:

NSTimeInterval is a double that already contains sub-second data after the decimal point. Depending what you need, your conversion could be a simple as multiplying by 1000.

- (void)testDateFormat
{
    NSDate *date = [NSDate date];
    NSLog(@"Time: %f", floor([date timeIntervalSince1970] * 1000));
    NSLog(@"Time: %f", floor([date timeIntervalSince1970]));
    NSLog(@"Time: %lli", [@(floor([date timeIntervalSince1970] * 1000)) longLongValue]);
    NSLog(@"Time: %lli", [@(floor([date timeIntervalSince1970])) longLongValue]);
}

// Result
// 2013-04-15 13:28:11.284 TestApp[10469:907] Time: 1366057691284.000000
// 2013-04-15 13:28:11.286 TestApp[10469:907] Time: 1366057691.000000
// 2013-04-15 13:28:11.287 TestApp[10469:907] Time: 1366057691284
// 2013-04-15 13:28:11.288 TestApp[10469:907] Time: 1366057691

回答2:

timeIntervalSince1970 will return seconds from 1970. There are other timeIntervalSince methods if needed.

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSDate_Class/Reference/Reference.html#//apple_ref/occ/instm/NSDate/timeIntervalSince1970

回答3:

timeIntervalSince1970 multiply the return value by 1000 because the returned value is in second not in millisecond kindly check that website for more testing http://currentmillis.com/