diff --git a/RCTAppleHealthKit/RCTAppleHealthKit+Queries.m b/RCTAppleHealthKit/RCTAppleHealthKit+Queries.m
index acc20be74383dbfc1486363787f4de6e7fc37913..45749d73ea62e694c91d1429e08e4abf7ccb972e 100644
--- a/RCTAppleHealthKit/RCTAppleHealthKit+Queries.m
+++ b/RCTAppleHealthKit/RCTAppleHealthKit+Queries.m
@@ -469,13 +469,13 @@
                                            NSDate *endDate = result.endDate;
                                            double value = [quantity doubleValueForUnit:unit];
 
-                                           NSString *startDateString = [RCTAppleHealthKit buildISO8601StringFromDate:startDate];
-                                           NSString *endDateString = [RCTAppleHealthKit buildISO8601StringFromDate:endDate];
+                                           int startDateTimestamp = [RCTAppleHealthKit buildTimestampFromDate:startDate];
+                                           int endDateTimestamp = [RCTAppleHealthKit buildTimestampFromDate:endDate];
 
                                            NSDictionary *elem = @{
                                                    @"value" : @(value),
-                                                   @"startDate" : startDateString,
-                                                   @"endDate" : endDateString,
+                                                   @"startDate" : @(startDateTimestamp),
+                                                   @"endDate" : @(endDateTimestamp),
                                            };
                                            [data addObject:elem];
                                        }