NSDate to Tick conversion

Question

I wanted to convert a date (nsdate) to tick values. Tick values are (1 Tick = 0.1 microseconds or 0.0001 milliseconds) since 1 Jan 0001 00:00:00 GMT. NSDate has functions like timeIntervalSince1970. So, how do I convert it?

Answer 1

I would like to share my experience:

I tried to find the seconds from 01/01/0001 and then multiply by 10,000,000. However, it gave me wrong results. So, I found out that 01/01/1970 is 621355968000000000 ticks from 01/01/0001 and used the following formula along with timeIntervalSince1970 function of NSDate.

Ticks = (MilliSeconds * 10000) + 621355968000000000

MilliSeconds = (Ticks - 621355968000000000) / 10000

Here is the outcome:

+(NSString *) dateToTicks:(NSDate *) date
{
    NSString *conversionDateStr = [self dateToYYYYMMDDString:date];
    NSDate *conversionDate = [self stringYYYYMMDDToDate:conversionDateStr];
    NSLog(@"%@",[date description]);
    NSLog(@"%@",[conversionDate description]);
    double tickFactor = 10000000;
    double timeSince1970 = [conversionDate timeIntervalSince1970];
    double doubleValue = (timeSince1970 * tickFactor ) + 621355968000000000;
    NSNumberFormatter *numberFormatter = [[[NSNumberFormatter alloc] init] autorelease];
    [numberFormatter setNumberStyle:NSNumberFormatterNoStyle];
    NSNumber *nsNumber = [NSNumber numberWithDouble:doubleValue];
    return [numberFormatter stringFromNumber:nsNumber];
}

Likewise, to convert from tick to date:

//MilliSeconds = (Ticks - 621355968000000000) / 10000
+(NSDate *) ticksToDate:(NSString *) ticks
{
    double tickFactor = 10000000;
    double ticksDoubleValue = [ticks doubleValue];
    double seconds = ((ticksDoubleValue - 621355968000000000)/ tickFactor);
    NSDate *returnDate = [NSDate dateWithTimeIntervalSince1970:seconds];
    NSLog(@"%@",[returnDate description]);
    return returnDate;
}