A very short test

  NSDate *timenow=[NSDate date];
    NSLog(@"Date before date2dot net=%@",[timenow description]);
  NSString *date2DotNet=[timenow dateToDotNet];
  NSLog(@"Dot net version of now = %@",date2DotNet);
  timenow=[NSDate dateFromDotNet:date2DotNet];
  NSLog(@"Date back from date2dot net=%@",[timenow description]);

NSDate+DotNetDates.h

#import <Foundation/Foundation.h>

@interface NSDate (DotNetDates)
+(NSDate*) dateFromDotNet:(NSString*)stringDate;
-(NSString*) dateToDotNet;
@end

SDate+DotNetDates.m

#import "NSDate+DotNetDates.h"

@implementation NSDate (DotNetDates)

+(NSDate*) dateFromDotNet:(NSString*)stringDate{
  
  NSDate *returnValue;
  
  if ([stringDate isMemberOfClass:[NSNull class]]) {
    returnValue=nil;
  }
  else  {
      NSInteger offset = [[NSTimeZone defaultTimeZone] secondsFromGMT];
  
      returnValue= [[NSDate dateWithTimeIntervalSince1970:
                       [[stringDate substringWithRange:NSMakeRange(6, 10)] intValue]]
                      dateByAddingTimeInterval:offset]; 
  }
       
       return returnValue;
       
}
-(NSString*) dateToDotNet{
  double timeSince1970=[self timeIntervalSince1970];
  NSInteger offset = [[NSTimeZone defaultTimeZone] secondsFromGMT];
  offset=offset/3600;
  double nowMillis = 1000.0 * (timeSince1970);
  NSString *dotNetDate=[NSString stringWithFormat:@"/Date(%.0f%+03d00)/",nowMillis,offset] ;
  return  dotNetDate;
}


@end