diff --git a/Bugsnag.podspec.json b/Bugsnag.podspec.json
index bb4769b0f..8afe0fcae 100644
--- a/Bugsnag.podspec.json
+++ b/Bugsnag.podspec.json
@@ -1,6 +1,6 @@
 {
   "name": "Bugsnag",
-  "version": "6.1.1",
+  "version": "6.1.2",
   "summary": "The Bugsnag crash reporting framework for Apple platforms.",
   "homepage": "https://bugsnag.com",
   "license": "MIT",
@@ -9,7 +9,7 @@
   },
   "source": {
     "git": "https://github.com/bugsnag/bugsnag-cocoa.git",
-    "tag": "v6.1.1"
+    "tag": "v6.1.2"
   },
   "frameworks": [
     "Foundation",
diff --git a/Bugsnag.xcodeproj/project.pbxproj b/Bugsnag.xcodeproj/project.pbxproj
index f02585c89..1716ee096 100644
--- a/Bugsnag.xcodeproj/project.pbxproj
+++ b/Bugsnag.xcodeproj/project.pbxproj
@@ -1480,7 +1480,6 @@
 				008969112486DAD000DC48C2 /* BSG_KSMachApple.h */,
 				008969122486DAD000DC48C2 /* BSG_KSString.h */,
 				008969132486DAD000DC48C2 /* BSG_KSMach.c */,
-				008969142486DAD000DC48C2 /* BSG_RFC3339DateTool.m */,
 				008969152486DAD000DC48C2 /* BSG_KSLogger.h */,
 				008969162486DAD000DC48C2 /* BSG_KSBacktrace_Private.h */,
 				008969172486DAD000DC48C2 /* BSG_KSMach_Arm64.c */,
@@ -1498,7 +1497,6 @@
 				008969242486DAD000DC48C2 /* BSG_KSString.c */,
 				008969252486DAD000DC48C2 /* BSG_KSObjC.c */,
 				008969262486DAD000DC48C2 /* BSG_KSLogger.m */,
-				008969272486DAD000DC48C2 /* BSG_RFC3339DateTool.h */,
 				008969282486DAD000DC48C2 /* BSG_KSMach.h */,
 			);
 			path = Tools;
@@ -1685,6 +1683,8 @@
 		00AD1CF524869EE500A27979 /* Helpers */ = {
 			isa = PBXGroup;
 			children = (
+				008969272486DAD000DC48C2 /* BSG_RFC3339DateTool.h */,
+				008969142486DAD000DC48C2 /* BSG_RFC3339DateTool.m */,
 				008968112486DA5600DC48C2 /* BSGSerialization.h */,
 				008968162486DA5600DC48C2 /* BSGSerialization.m */,
 				008968102486DA5600DC48C2 /* BugsnagCollections.h */,
diff --git a/Bugsnag/BSGOutOfMemoryWatchdog.m b/Bugsnag/BSGOutOfMemoryWatchdog.m
index fce581182..76bea98e7 100644
--- a/Bugsnag/BSGOutOfMemoryWatchdog.m
+++ b/Bugsnag/BSGOutOfMemoryWatchdog.m
@@ -16,6 +16,7 @@
 #import "BugsnagSessionTracker.h"
 #import "Private.h"
 #import "BugsnagErrorTypes.h"
+#import "BSG_RFC3339DateTool.h"
 
 @interface BSGOutOfMemoryWatchdog ()
 @property(nonatomic, getter=isWatching) BOOL watching;
@@ -26,10 +27,6 @@ @interface BSGOutOfMemoryWatchdog ()
 @property(nonatomic) NSString *codeBundleId;
 @end
 
-@interface Bugsnag ()
-+ (NSDateFormatter *_Nonnull)payloadDateFormatter;
-@end
-
 @implementation BSGOutOfMemoryWatchdog
 
 - (instancetype)init {
@@ -152,7 +149,7 @@ - (void)handleTransitionToBackground:(NSNotification *)note {
 }
 
 - (void)handleLowMemoryChange:(NSNotification *)note {
-    self.cachedFileInfo[@"device"][@"lowMemory"] = [[Bugsnag payloadDateFormatter]
+    self.cachedFileInfo[@"device"][@"lowMemory"] = [BSG_RFC3339DateTool
                                                     stringFromDate:[NSDate date]];
     [self writeSentinelFile];
 }
diff --git a/Bugsnag/Bugsnag.m b/Bugsnag/Bugsnag.m
index 879de84ba..995afbfc4 100644
--- a/Bugsnag/Bugsnag.m
+++ b/Bugsnag/Bugsnag.m
@@ -210,17 +210,6 @@ + (BOOL)resumeSession {
     }
 }
 
-+ (NSDateFormatter *)payloadDateFormatter {
-    static NSDateFormatter *formatter;
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-      formatter = [NSDateFormatter new];
-      formatter.dateFormat = @"yyyy'-'MM'-'dd'T'HH':'mm':'ssZZZ";
-      formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
-    });
-    return formatter;
-}
-
 + (void)addRuntimeVersionInfo:(NSString *)info
                       withKey:(NSString *)key {
     if ([self bugsnagStarted]) {
diff --git a/Bugsnag/Client/BugsnagClient.m b/Bugsnag/Client/BugsnagClient.m
index 3c31ed6b7..60e426085 100644
--- a/Bugsnag/Client/BugsnagClient.m
+++ b/Bugsnag/Client/BugsnagClient.m
@@ -353,10 +353,6 @@ @interface BugsnagUser ()
 - (instancetype)initWithDictionary:(NSDictionary *)dict;
 @end
 
-@interface Bugsnag ()
-+ (NSDateFormatter *_Nonnull)payloadDateFormatter;
-@end
-
 @interface BugsnagBreadcrumbs ()
 @property(nonatomic, readwrite, strong) NSMutableArray *breadcrumbs;
 @end
@@ -1177,7 +1173,7 @@ - (void)orientationChanged:(NSNotification *)notification {
 }
 
 - (void)lowMemoryWarning:(NSNotification *)notif {
-    [self.state addMetadata:[[Bugsnag payloadDateFormatter] stringFromDate:[NSDate date]]
+    [self.state addMetadata:[BSG_RFC3339DateTool stringFromDate:[NSDate date]]
                       withKey:BSEventLowMemoryWarning
                     toSection:BSGKeyDeviceState];
      
diff --git a/Bugsnag/Delivery/BugsnagSessionTrackingApiClient.m b/Bugsnag/Delivery/BugsnagSessionTrackingApiClient.m
index f709f9aa2..b087b6c46 100644
--- a/Bugsnag/Delivery/BugsnagSessionTrackingApiClient.m
+++ b/Bugsnag/Delivery/BugsnagSessionTrackingApiClient.m
@@ -50,12 +50,15 @@ - (void)deliverSessionsInStore:(BugsnagSessionFileStore *)store {
     NSDictionary<NSString *, NSDictionary *> *filesWithIds = [store allFilesByName];
 
     for (NSString *fileId in [filesWithIds allKeys]) {
-        // skip dupe requests
-        if ([self isActiveRequest:fileId]) {
-            continue;
+
+        // De-duplicate files as deletion of the file is asynchronous and so multiple calls
+        // to this method will result in multiple send requests
+        @synchronized (self.activeIds) {
+            if ([self.activeIds containsObject:fileId]) {
+                continue;
+            }
+            [self.activeIds addObject:fileId];
         }
-        // add request
-        [self.activeIds addObject:fileId];
 
         BugsnagSession *session = [[BugsnagSession alloc] initWithDictionary:filesWithIds[fileId]];
 
@@ -64,7 +67,6 @@ - (void)deliverSessionsInStore:(BugsnagSessionFileStore *)store {
                 initWithSessions:@[session]
                           config:[Bugsnag configuration]
                     codeBundleId:self.codeBundleId];
-            NSUInteger sessionCount = payload.sessions.count;
             NSMutableDictionary *data = [payload toJson];
             NSDictionary *HTTPHeaders = @{
                     @"Bugsnag-Payload-Version": @"1.0",
@@ -77,26 +79,19 @@ - (void)deliverSessionsInStore:(BugsnagSessionFileStore *)store {
                     headers:HTTPHeaders
                onCompletion:^(NSUInteger sentCount, BOOL success, NSError *error) {
                    if (success && error == nil) {
-                       bsg_log_info(@"Sent %lu sessions to Bugsnag", (unsigned long) sessionCount);
+                       bsg_log_info(@"Sent session %@ to Bugsnag", session.id);
                        [store deleteFileWithId:fileId];
                    } else {
                        bsg_log_warn(@"Failed to send sessions to Bugsnag: %@", error);
                    }
 
                    // remove request
-                   [self.activeIds removeObject:fileId];
+                   @synchronized (self.activeIds) {
+                       [self.activeIds removeObject:fileId];
+                   }
                }];
         }];
     }
 }
 
-- (BOOL)isActiveRequest:(NSString *)fileId {
-    for (NSString *val in self.activeIds) {
-        if ([val isEqualToString:fileId]) {
-            return true;
-        }
-    }
-    return false;
-}
-
 @end
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/Tools/BSG_RFC3339DateTool.h b/Bugsnag/Helpers/BSG_RFC3339DateTool.h
similarity index 100%
rename from Bugsnag/KSCrash/Source/KSCrash/Recording/Tools/BSG_RFC3339DateTool.h
rename to Bugsnag/Helpers/BSG_RFC3339DateTool.h
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/Tools/BSG_RFC3339DateTool.m b/Bugsnag/Helpers/BSG_RFC3339DateTool.m
similarity index 61%
rename from Bugsnag/KSCrash/Source/KSCrash/Recording/Tools/BSG_RFC3339DateTool.m
rename to Bugsnag/Helpers/BSG_RFC3339DateTool.m
index 26f5e44bf..99b5a0f1a 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/Tools/BSG_RFC3339DateTool.m
+++ b/Bugsnag/Helpers/BSG_RFC3339DateTool.m
@@ -24,14 +24,18 @@
 
 #import "BSG_RFC3339DateTool.h"
 
+@interface BSG_RFC3339DateTool ()
++ (NSDateFormatter *)iosFormatterInstance;
+@end
+
 @implementation BSG_RFC3339DateTool
 
-static NSString *const kDateFormatterKey = @"RfcDateFormatter";
+static NSString *const kRfcDateFormatterKey = @"RfcDateFormatter";
+static NSString *const kIsoDateFormatterKey = @"IsoDateFormatter";
 
 + (NSDateFormatter *)sharedInstance {
     NSMutableDictionary *threadDict = [[NSThread currentThread] threadDictionary];
-    NSDateFormatter *formatter = threadDict[kDateFormatterKey];
-        
+    NSDateFormatter *formatter = threadDict[kRfcDateFormatterKey];
     if (formatter == nil) {
         formatter = [NSDateFormatter new];
         NSLocale *locale =
@@ -39,8 +43,30 @@ + (NSDateFormatter *)sharedInstance {
         [formatter setLocale:locale];
         [formatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"];
         [formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
-        threadDict[kDateFormatterKey] = formatter;
+        threadDict[kRfcDateFormatterKey] = formatter;
     }
+
+    formatter = threadDict[kRfcDateFormatterKey];
+    return formatter;
+}
+
+/**
+Used internally to convert any dates with timezones (from older notifier versions) to Zulu time
+ */
++ (NSDateFormatter *)iosFormatterInstance {
+    NSMutableDictionary *threadDict = [[NSThread currentThread] threadDictionary];
+    NSDateFormatter *formatter = threadDict[kIsoDateFormatterKey];
+    if (formatter == nil) {
+        formatter = [NSDateFormatter new];
+        NSLocale *locale =
+        [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
+        [formatter setLocale:locale];
+        [formatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ssZZZ"];
+        [formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
+        threadDict[kIsoDateFormatterKey] = formatter;
+    }
+    
+    formatter = threadDict[kIsoDateFormatterKey];
     return formatter;
 }
 
@@ -55,7 +81,11 @@ + (NSDate *)dateFromString:(NSString *)string {
     if (![string isKindOfClass:[NSString class]]) {
         return nil;
     }
-    return [[self sharedInstance] dateFromString:string];
+    NSDate *date = [[self sharedInstance] dateFromString:string];
+    if (!date) {
+        date = [[self iosFormatterInstance] dateFromString:string];
+    }
+    return date;
 }
 
 + (NSString *)stringFromUNIXTimestamp:(unsigned long long)timestamp {
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.h b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.h
index b9a31ac82..b442c1382 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.h
+++ b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.h
@@ -119,6 +119,11 @@
  */
 - (NSArray<BugsnagThread *> *)captureThreads:(NSException *)exc depth:(int)depth;
 
+/**
+ * Collects information about the application's foreground state (duration in foreground/background)
+ */
+- (NSDictionary *)captureAppStats;
+
 /** If YES, reports will be sent even if a debugger is attached
  *
  * Default: NO
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.m b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.m
index 77f8400ff..55390ccad 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.m
+++ b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrash.m
@@ -39,6 +39,8 @@
 #import "BugsnagThread.h"
 #import "BSGSerialization.h"
 #import "BugsnagErrorReportSink.h"
+#import "BugsnagCollections.h"
+#import "BSG_KSCrashReportFields.h"
 
 #if BSG_HAS_UIKIT
 #import <UIKit/UIKit.h>
@@ -320,6 +322,16 @@ - (void)sendAllReports {
     return @[];
 }
 
+- (NSDictionary *)captureAppStats {
+    BSG_KSCrash_State state = crashContext()->state;
+    bsg_kscrashstate_updateDurationStats(&state);
+    NSMutableDictionary *dict = [NSMutableDictionary new];
+    BSGDictSetSafeObject(dict, @(state.activeDurationSinceLaunch), @BSG_KSCrashField_ActiveTimeSinceLaunch);
+    BSGDictSetSafeObject(dict, @(state.backgroundDurationSinceLaunch), @BSG_KSCrashField_BGTimeSinceLaunch);
+    BSGDictSetSafeObject(dict, @(state.applicationIsInForeground), @BSG_KSCrashField_AppInFG);
+    return dict;
+}
+
 - (void)reportUserException:(NSString *)name
                      reason:(NSString *)reason
                handledState:(NSDictionary *)handledState
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashC.c b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashC.c
index 61ec57190..f076b79a7 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashC.c
+++ b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashC.c
@@ -243,5 +243,4 @@ char *bsg_kscrash_captureThreadTrace(int discardDepth, int frameCount, uintptr_t
         bsg_kscrashsentry_resume_threads_user(false);
     }
     return trace;
-    
 }
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.h b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.h
index f5368e058..192f85eb6 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.h
+++ b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.h
@@ -121,6 +121,14 @@ void bsg_kscrashstate_notifyAppCrash(BSG_KSCrashType type);
  */
 const BSG_KSCrash_State *bsg_kscrashstate_currentState(void);
 
+/**
+ * Updates the stats for duration in foreground/background. This needs to
+ * be updated whenever an error report is captured.
+ *
+ * @param state the kscrash state
+ */
+void bsg_kscrashstate_updateDurationStats(BSG_KSCrash_State *const state);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.m b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.m
index 9ed3e31fb..57e6ba340 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.m
+++ b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSCrashState.m
@@ -356,7 +356,15 @@ void bsg_kscrashstate_notifyAppTerminate(void) {
 void bsg_kscrashstate_notifyAppCrash(BSG_KSCrashType type) {
     BSG_KSCrash_State *const state = bsg_g_state;
     const char *const stateFilePath = bsg_g_stateFilePath;
+    bsg_kscrashstate_updateDurationStats(state);
+    BOOL didCrash = type != BSG_KSCrashTypeUserReported;
+    state->crashedThisLaunch |= didCrash;
+    if (didCrash) {
+        bsg_kscrashstate_i_saveState(state, stateFilePath);
+    }
+}
 
+void bsg_kscrashstate_updateDurationStats(BSG_KSCrash_State *const state) {
     const double duration = bsg_ksmachtimeDifferenceInSeconds(
         mach_absolute_time(), state->appStateTransitionTime);
     if (state->applicationIsActive) {
@@ -366,11 +374,6 @@ void bsg_kscrashstate_notifyAppCrash(BSG_KSCrashType type) {
         state->backgroundDurationSinceLaunch += duration;
         state->backgroundDurationSinceLastCrash += duration;
     }
-    BOOL didCrash = type != BSG_KSCrashTypeUserReported;
-    state->crashedThisLaunch |= didCrash;
-    if (didCrash) {
-        bsg_kscrashstate_i_saveState(state, stateFilePath);
-    }
 }
 
 const BSG_KSCrash_State *bsg_kscrashstate_currentState(void) {
diff --git a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSSystemInfo.m b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSSystemInfo.m
index 109ecac92..af11e3e0c 100644
--- a/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSSystemInfo.m
+++ b/Bugsnag/KSCrash/Source/KSCrash/Recording/BSG_KSSystemInfo.m
@@ -38,6 +38,7 @@
 #import "BSG_KSLogger.h"
 #import "BSG_KSCrashReportFields.h"
 #import "BSG_KSMach.h"
+#import "BSG_KSCrash.h"
 
 #import <CommonCrypto/CommonDigest.h>
 #if BSG_PLATFORM_IOS || BSG_PLATFORM_TVOS
@@ -416,6 +417,8 @@ + (NSDictionary *)systemInfo {
     };
     BSGDictSetSafeObject(sysInfo, memory, @BSG_KSSystemField_Memory);
 
+    NSDictionary *statsInfo = [[BSG_KSCrash sharedInstance] captureAppStats];
+    BSGDictSetSafeObject(sysInfo, statsInfo, @BSG_KSCrashField_AppStats);
     return sysInfo;
 }
 
diff --git a/Bugsnag/Payload/BugsnagBreadcrumb.m b/Bugsnag/Payload/BugsnagBreadcrumb.m
index 8c2ff6c91..655774c28 100644
--- a/Bugsnag/Payload/BugsnagBreadcrumb.m
+++ b/Bugsnag/Payload/BugsnagBreadcrumb.m
@@ -23,6 +23,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 //
+#import "BSG_RFC3339DateTool.h"
+
 #import "BugsnagBreadcrumb.h"
 #import "BugsnagBreadcrumbs.h"
 #import "Bugsnag.h"
@@ -72,10 +74,6 @@ BSGBreadcrumbType BSGBreadcrumbTypeFromString(NSString *value) {
     }
 }
 
-@interface Bugsnag ()
-+ (NSDateFormatter *_Nonnull)payloadDateFormatter;
-@end
-
 @implementation BugsnagBreadcrumb
 
 - (instancetype)init {
@@ -93,8 +91,7 @@ - (BOOL)isValid {
 
 - (NSDictionary *)objectValue {
     @synchronized (self) {
-        NSString *timestamp =
-        [[Bugsnag payloadDateFormatter] stringFromDate:_timestamp];
+        NSString *timestamp = [BSG_RFC3339DateTool stringFromDate:_timestamp];
         if (timestamp && _message.length > 0) {
             NSMutableDictionary *metadata = [NSMutableDictionary new];
             for (NSString *key in _metadata) {
@@ -212,7 +209,7 @@ + (instancetype)breadcrumbFromDict:(NSDictionary *)dict {
         return [self breadcrumbWithBlock:^(BugsnagBreadcrumb *crumb) {
             crumb.message = dict[BSGKeyMessage] ?: dict[BSGKeyName];
             crumb.metadata = dict[BSGKeyMetadata] ?: dict[@"metadata"];
-            crumb.timestamp = [[Bugsnag payloadDateFormatter] dateFromString:dict[BSGKeyTimestamp]];
+            crumb.timestamp = [BSG_RFC3339DateTool dateFromString:dict[BSGKeyTimestamp]];
             crumb.type = BSGBreadcrumbTypeFromString(dict[BSGKeyType]);
         }];
     }
diff --git a/Bugsnag/Payload/BugsnagDeviceWithState.m b/Bugsnag/Payload/BugsnagDeviceWithState.m
index 2ed38dc3f..5c939a913 100644
--- a/Bugsnag/Payload/BugsnagDeviceWithState.m
+++ b/Bugsnag/Payload/BugsnagDeviceWithState.m
@@ -7,6 +7,7 @@
 //
 
 #import "BugsnagPlatformConditional.h"
+#import "BSG_RFC3339DateTool.h"
 
 #import "BugsnagDeviceWithState.h"
 #import "BugsnagCollections.h"
@@ -53,10 +54,6 @@
     return freeBytes;
 }
 
-@interface Bugsnag ()
-+ (NSDateFormatter *)payloadDateFormatter;
-@end
-
 @interface BugsnagDevice ()
 + (void)populateFields:(BugsnagDevice *)device
             dictionary:(NSDictionary *)event;
@@ -64,19 +61,8 @@ + (void)populateFields:(BugsnagDevice *)device
 - (NSDictionary *)toDictionary;
 @end
 
-@interface BugsnagDeviceWithState ()
-@property (nonatomic, readonly) NSDateFormatter *formatter;
-@end
-
 @implementation BugsnagDeviceWithState
 
-- (instancetype)init {
-    if (self = [super init]) {
-        _formatter = [Bugsnag payloadDateFormatter];
-    }
-    return self;
-}
-
 + (BugsnagDeviceWithState *) deviceFromJson:(NSDictionary *)json {
     BugsnagDeviceWithState *device = [BugsnagDeviceWithState new];
     device.id = json[@"id"];
@@ -99,7 +85,7 @@ + (BugsnagDeviceWithState *) deviceFromJson:(NSDictionary *)json {
 
     id time = json[@"time"];
     if (time && [time isKindOfClass:[NSString class]]) {
-        device.time = [device.formatter dateFromString:time];
+        device.time = [BSG_RFC3339DateTool dateFromString:time];
     }
     return device;
 }
@@ -125,7 +111,7 @@ + (BugsnagDeviceWithState *)deviceWithDictionary:(NSDictionary *)event {
     NSString *val = [event valueForKeyPath:@"report.timestamp"];
 
     if (val != nil) {
-        device.time = [device.formatter dateFromString:val];
+        device.time = [BSG_RFC3339DateTool dateFromString:val];
     }
     return device;
 }
@@ -138,7 +124,7 @@ - (NSDictionary *)toDictionary {
     BSGDictInsertIfNotNil(dict, self.orientation, @"orientation");
 
     if (self.time != nil) {
-        BSGDictInsertIfNotNil(dict, [self.formatter stringFromDate:self.time], @"time");
+        BSGDictInsertIfNotNil(dict, [BSG_RFC3339DateTool stringFromDate:self.time], @"time");
     }
     return dict;
 }
diff --git a/Bugsnag/Payload/BugsnagNotifier.m b/Bugsnag/Payload/BugsnagNotifier.m
index c028b45d4..d07cbe9ac 100644
--- a/Bugsnag/Payload/BugsnagNotifier.m
+++ b/Bugsnag/Payload/BugsnagNotifier.m
@@ -23,7 +23,7 @@ - (instancetype)init {
 #else
         self.name = @"Bugsnag Objective-C";
 #endif
-        self.version = @"6.1.1";
+        self.version = @"6.1.2";
         self.url = @"https://github.com/bugsnag/bugsnag-cocoa";
         self.dependencies = [NSMutableArray new];
     }
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fc52938e4..55b2ebd69 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,19 @@
 Changelog
 =========
 
+## 6.1.2 (2020-07-21)
+
+### Bug fixes
+
+* Ensure foreground stats are recorded for handled errors
+  [#755](https://github.com/bugsnag/bugsnag-cocoa/pull/755)
+
+* Synchronize access to sessions being delivered in de-duplication code
+  [#756](https://github.com/bugsnag/bugsnag-cocoa/pull/756)
+
+* Removed non-thread safe date formatter
+  [#758](https://github.com/bugsnag/bugsnag-cocoa/pull/758)
+
 ## 6.1.1 (2020-07-16)
 
 ### Bug fixes
diff --git a/Tests/BugsnagClientMirrorTest.m b/Tests/BugsnagClientMirrorTest.m
index 8876734cc..c6d8039d5 100644
--- a/Tests/BugsnagClientMirrorTest.m
+++ b/Tests/BugsnagClientMirrorTest.m
@@ -124,7 +124,6 @@ - (void)setUp {
     self.clientWhitelist = [NSSet setWithArray:@[
             @"startWithApiKey: @24@0:8@16",
             @"startWithConfiguration: @24@0:8@16",
-            @"payloadDateFormatter @16@0:8",
             @"updateCodeBundleId: v24@0:8@16",
             @"instance @16@0:8",
             @"client @16@0:8",
diff --git a/Tests/BugsnagErrorReportSinkTests.m b/Tests/BugsnagErrorReportSinkTests.m
index 96ceaf328..582751d0f 100644
--- a/Tests/BugsnagErrorReportSinkTests.m
+++ b/Tests/BugsnagErrorReportSinkTests.m
@@ -309,7 +309,7 @@ - (void)testEventDevice {
     XCTAssertEqualObjects(device[@"jailbroken"], @YES);
     XCTAssertEqualObjects(device[@"freeMemory"], @742920192);
     XCTAssertEqualObjects(device[@"orientation"], @"unknown");
-    XCTAssertEqualObjects(device[@"time"], @"2014-12-02T01:56:13+0000");
+    XCTAssertEqualObjects(device[@"time"], @"2014-12-02T01:56:13Z");
 }
 
 - (void)testEventApp {
diff --git a/Tests/BugsnagEventPersistLoadTest.m b/Tests/BugsnagEventPersistLoadTest.m
index c4cd122a1..18edd0182 100644
--- a/Tests/BugsnagEventPersistLoadTest.m
+++ b/Tests/BugsnagEventPersistLoadTest.m
@@ -17,9 +17,6 @@
 #import "BugsnagHandledState.h"
 #import "Bugsnag.h"
 
-@interface Bugsnag ()
-+ (NSDateFormatter *)payloadDateFormatter;
-@end
 #import "BugsnagError.h"
 #import "BugsnagStackframe.h"
 #import "BugsnagThread.h"
@@ -170,6 +167,10 @@ - (void)testDeviceFieldsOverride {
                     }
             }
     }];
+    
+    NSDateFormatter *formatter = [NSDateFormatter new];
+    formatter.dateFormat = @"yyyy'-'MM'-'dd'T'HH':'mm':'ssZZZ";
+    formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
 
     BugsnagDeviceWithState *device = event.device;
     XCTAssertEqualObjects(@920234094, device.freeDisk);
@@ -177,7 +178,7 @@ - (void)testDeviceFieldsOverride {
     XCTAssertEqualObjects(@92092340923, device.totalMemory);
     XCTAssertEqualObjects(@"landscape", device.orientation);
     XCTAssertFalse(device.jailbroken);
-    NSString *date = [device.formatter stringFromDate:device.time];
+    NSString *date = [formatter stringFromDate:device.time];
     XCTAssertEqualObjects(@"2020-05-11T15:36:09+0000", date);
 
     XCTAssertEqualObjects(@"f0a9b99", device.id);
@@ -264,7 +265,11 @@ - (void)testBreadcrumbsOverride {
     XCTAssertEqual(1, [event.breadcrumbs count]);
     XCTAssertEqual(BSGBreadcrumbTypeManual, breadcrumb.type);
     XCTAssertEqualObjects(@"installed NDK", breadcrumb.message);
-    NSDate *date = [[Bugsnag payloadDateFormatter] dateFromString:@"2020-02-14T16:12:23+001"];
+    
+    NSDateFormatter *formatter = [NSDateFormatter new];
+    formatter.dateFormat = @"yyyy'-'MM'-'dd'T'HH':'mm':'ssZZZ";
+    formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
+    NSDate *date = [formatter dateFromString:@"2020-02-14T16:12:23+001"];
     XCTAssertEqualObjects(date, breadcrumb.timestamp);
     XCTAssertEqualObjects(@{
             @"custom": @{
@@ -348,8 +353,11 @@ - (void)testSessionOverride {
                     }
             }
     }];
-
-    NSDate *date = [[Bugsnag payloadDateFormatter] dateFromString:@"2020-05-18T13:13:24Z"];
+    
+    NSDateFormatter *formatter = [NSDateFormatter new];
+    formatter.dateFormat = @"yyyy'-'MM'-'dd'T'HH':'mm':'ssZZZ";
+    formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
+    NSDate *date = [formatter dateFromString:@"2020-05-18T13:13:24Z"];
     XCTAssertEqualObjects(date, event.session.startedAt);
     XCTAssertEqualObjects(@"123", event.session.id);
     XCTAssertEqual(1, event.session.unhandledCount);
diff --git a/Tests/KSCrash/RFC3339DateTool_Tests.m b/Tests/KSCrash/RFC3339DateTool_Tests.m
index bd2b9791a..523283d8a 100755
--- a/Tests/KSCrash/RFC3339DateTool_Tests.m
+++ b/Tests/KSCrash/RFC3339DateTool_Tests.m
@@ -68,6 +68,25 @@ - (void) testDateFromString
     XCTAssertEqualObjects(actual, expected, @"");
 }
 
+- (void) testDateFromStringWithTimezone
+{
+    NSDate* expected = [self gmtDateWithYear:2000 month:1 day:2 hour:3 minute:4 second:5];
+    NSDate* actual = [BSG_RFC3339DateTool dateFromString:@"2000-01-02T03:04:05+0000"];
+
+    XCTAssertEqualObjects(actual, expected, @"");
+}
+
+- (void) testDateFromStringWithTimezonePlus2
+{
+    NSDate* expected = [self gmtDateWithYear:2000 month:1 day:2 hour:1 minute:4 second:5];
+    NSDate* actual = [BSG_RFC3339DateTool dateFromString:@"2000-01-02T03:04:05+0200"];
+
+    XCTAssertEqualObjects(actual, expected, @"");
+    
+    // Convert back again to verify overall effect
+    XCTAssertEqualObjects([BSG_RFC3339DateTool stringFromDate:actual], @"2000-01-02T01:04:05Z");
+}
+
 - (void) testStringFromUnixTimestamp
 {
     NSDate* date = [self gmtDateWithYear:2000 month:1 day:2 hour:3 minute:4 second:5];
diff --git a/Tests/report.json b/Tests/report.json
index 8df5f3cfc..d5e5bcfc6 100644
--- a/Tests/report.json
+++ b/Tests/report.json
@@ -2103,8 +2103,8 @@
                 "depth": 4,
                 "severity": "warning",
                 "breadcrumbs": [
-                    {"message": "App launched", "timestamp": "2020-02-14T16:12:22+0000", "type": "manual", "metaData":{}},
-                    {"message": "Tapped button", "timestamp": "2020-02-14T16:12:24+0000", "type": "manual", "metaData":{}}
+                    {"message": "App launched", "timestamp": "2020-02-14T16:12:22Z", "type": "manual", "metaData":{}},
+                    {"message": "Tapped button", "timestamp": "2020-02-14T16:12:24Z", "type": "manual", "metaData":{}}
                 ]
             }
         }
diff --git a/VERSION b/VERSION
index 132c6def5..5e3254243 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-6.1.1
\ No newline at end of file
+6.1.2