Index: src/OFGZIPStream.h
==================================================================
--- src/OFGZIPStream.h
+++ src/OFGZIPStream.h
@@ -38,11 +38,11 @@
 		OF_GZIP_STREAM_ID2,
 		OF_GZIP_STREAM_COMPRESSION_METHOD,
 		OF_GZIP_STREAM_FLAGS,
 		OF_GZIP_STREAM_MODIFICATION_TIME,
 		OF_GZIP_STREAM_EXTRA_FLAGS,
-		OF_GZIP_STREAM_OS,
+		OF_GZIP_STREAM_OPERATING_SYSTEM,
 		OF_GZIP_STREAM_EXTRA_LENGTH,
 		OF_GZIP_STREAM_EXTRA,
 		OF_GZIP_STREAM_NAME,
 		OF_GZIP_STREAM_COMMENT,
 		OF_GZIP_STREAM_HEADER_CRC16,
@@ -56,34 +56,51 @@
 		OF_GZIP_STREAM_FLAG_EXTRA	 = 0x04,
 		OF_GZIP_STREAM_FLAG_NAME	 = 0x08,
 		OF_GZIP_STREAM_FLAG_COMMENT	 = 0x10
 	} _flags;
 	uint8_t _extraFlags;
-	enum of_gzip_stream_os {
-		OF_GZIP_STREAM_OS_FAT		=   0,
-		OF_GZIP_STREAM_OS_AMIGA		=   1,
-		OF_GZIP_STREAM_OS_VMS		=   2,
-		OF_GZIP_STREAM_OS_UNIX		=   3,
-		OF_GZIP_STREAM_OS_VM_CMS	=   4,
-		OF_GZIP_STREAM_OS_ATARI_TOS	=   5,
-		OF_GZIP_STREAM_OS_HPFS		=   6,
-		OF_GZIP_STREAM_OS_MACINTOSH	=   7,
-		OF_GZIP_STREAM_OS_Z_SYSTEM	=   8,
-		OF_GZIP_STREAM_OS_CP_M		=   9,
-		OF_GZIP_STREAM_OS_TOPS_20	=  10,
-		OF_GZIP_STREAM_OS_NTFS		=  11,
-		OF_GZIP_STREAM_OS_QDO		=  12,
-		OF_GZIP_STREAM_OS_ACORN_RISC_OS	=  13,
-		OF_GZIP_STREAM_OS_UNKNOWN	= 255
-	} _OS;
+	enum of_gzip_stream_operating_system {
+		OF_GZIP_STREAM_OPERATING_SYSTEM_FAT		=   0,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_AMIGA		=   1,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_VMS		=   2,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_UNIX		=   3,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_VM_CMS		=   4,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_ATARI_TOS	=   5,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_HPFS		=   6,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_MACINTOSH	=   7,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_Z_SYSTEM	=   8,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_CP_M		=   9,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_TOPS_20		=  10,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_NTFS		=  11,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_QDO		=  12,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_ACORN_RISC_OS	=  13,
+		OF_GZIP_STREAM_OPERATING_SYSTEM_UNKNOWN		= 255
+	} _operatingSystemMadeOn;
 	size_t _bytesRead;
 	uint8_t _buffer[4];
 	OFDate *_Nullable _modificationDate;
 	uint16_t _extraLength;
 	uint32_t _CRC32, _uncompressedSize;
 }
 
+/*!
+ * @brief The operating system on which the data was compressed.
+ *
+ * This property is only guaranteed to be available once @ref atEndOfStream is
+ * true.
+ */
+@property (readonly, nonatomic)
+    enum of_gzip_stream_operating_system operatingSystemMadeOn;
+
+/*!
+ * @brief The modification date of the original file.
+ *
+ * This property is only guaranteed to be available once @ref atEndOfStream is
+ * true.
+ */
+@property OF_NULLABLE_PROPERTY (readonly, nonatomic) OFDate *modificationDate;
+
 /*!
  * @brief Creates a new OFGZIPStream with the specified underlying stream.
  *
  * @param stream The underlying stream for the OFGZIPStream
  * @param mode The mode for the OFGZIPStream. Valid modes are "r" for reading

Index: src/OFGZIPStream.m
==================================================================
--- src/OFGZIPStream.m
+++ src/OFGZIPStream.m
@@ -28,10 +28,13 @@
 #import "OFNotImplementedException.h"
 #import "OFNotOpenException.h"
 #import "OFTruncatedDataException.h"
 
 @implementation OFGZIPStream
+@synthesize operatingSystemMadeOn = _operatingSystemMadeOn;
+@synthesize modificationDate = _modificationDate;
+
 + (instancetype)streamWithStream: (OFStream *)stream
 			    mode: (OFString *)mode
 {
 	return [[[self alloc] initWithStream: stream
 					mode: mode] autorelease];
@@ -52,10 +55,12 @@
 			@throw [OFNotImplementedException
 			    exceptionWithSelector: _cmd
 					   object: nil];
 
 		_stream = [stream retain];
+		_operatingSystemMadeOn =
+		    OF_GZIP_STREAM_OPERATING_SYSTEM_UNKNOWN;
 		_CRC32 = ~0;
 	} @catch (id e) {
 		[self release];
 		@throw e;
 	}
@@ -140,16 +145,16 @@
 				return 0;
 
 			_extraFlags = byte;
 			_state++;
 			break;
-		case OF_GZIP_STREAM_OS:
+		case OF_GZIP_STREAM_OPERATING_SYSTEM:
 			if ([_stream readIntoBuffer: &byte
 					     length: 1] < 1)
 				return 0;
 
-			_OS = byte;
+			_operatingSystemMadeOn = byte;
 			_state++;
 			break;
 		case OF_GZIP_STREAM_EXTRA_LENGTH:
 			if (!(_flags & OF_GZIP_STREAM_FLAG_EXTRA)) {
 				_state += 2;