diff --git a/contrib/calendar/calendar.factor b/contrib/calendar/calendar.factor
index a329c206d3..081b150361 100644
--- a/contrib/calendar/calendar.factor
+++ b/contrib/calendar/calendar.factor
@@ -1,16 +1,10 @@
+IN: calendar
 USING: arrays errors generic hashtables io kernel math
 namespaces sequences strings prettyprint inspector ;
-IN: calendar
 
 TUPLE: timestamp year month day hour minute second gmt-offset ;
 TUPLE: dt year month day hour minute second ;
 
-SYMBOL: gmt-offset
--6 gmt-offset set-global  ! central time
-
-LIBRARY: libc
-FUNCTION: time_t time ( time_t* t ) ;
-
 : month-names
     {
         "Not a month" "January" "February" "March" "April" "May" "June"
@@ -198,7 +192,7 @@ M: number +second ( timestamp n -- timestamp )
     over set-timestamp-gmt-offset ;
 
 : >local-time ( timestamp -- timestamp )
-    gmt-offset get convert-timezone ;
+    gmt-offset convert-timezone ;
 
 : >gmt ( timestamp -- timestamp )
     0 convert-timezone ;
@@ -283,3 +277,4 @@ M: number +second ( timestamp n -- timestamp )
         dup timestamp-minute unparse 2 CHAR: 0 pad-left write ":" write
         timestamp-second >fixnum unparse 2 CHAR: 0 pad-left write " GMT" write
     ] string-out ;
+
diff --git a/contrib/calendar/load.factor b/contrib/calendar/load.factor
index 6fedb3dae4..9c7b93cea4 100644
--- a/contrib/calendar/load.factor
+++ b/contrib/calendar/load.factor
@@ -1,13 +1,15 @@
-USING: kernel modules sequences ;
-"calendar"
+USING: kernel modules namespaces sequences ;
 
-{
-    { [ win32? ] [ { "os-win32.factor" } ] }
-    { [ t ] [ { "os-unix.factor" } ] }
-} cond
-{
-    "calendar.factor" 
-} append
+"calendar"
+[
+    {
+        { [ unix? macosx? not and ] [ "os-unix.factor" , "os-linux.factor" , ] }
+        { [ macosx? ] [ "os-unix.factor" , "os-macosx.factor" , ] }
+        { [ unix? ] [ "os-unix.factor" , ] }
+        { [ win32? ] [ "os-win32.factor" , ] }
+    } cond
+    "calendar.factor" ,
+] { } make
 
 { "test/calendar.factor" }
 provide
diff --git a/contrib/calendar/os-linux.factor b/contrib/calendar/os-linux.factor
new file mode 100644
index 0000000000..82d05ecb2a
--- /dev/null
+++ b/contrib/calendar/os-linux.factor
@@ -0,0 +1,15 @@
+IN: calendar
+
+
+BEGIN-STRUCT: tm
+    FIELD: int sec     ! Seconds: 0-59 (K&R says 0-61?)
+    FIELD: int min     ! Minutes: 0-59
+    FIELD: int hour    ! Hours since midnight: 0-23
+    FIELD: int mday    ! Day of the month: 1-31
+    FIELD: int mon     ! Months *since* january: 0-11
+    FIELD: int year    ! Years since 1900
+    FIELD: int wday    ! Days since Sunday (0-6)
+    FIELD: int yday    ! Days since Jan. 1: 0-365
+    FIELD: int isdst   ! +1 Daylight Savings Time, 0 No DST,
+END-STRUCT
+
diff --git a/contrib/calendar/os-macosx.factor b/contrib/calendar/os-macosx.factor
new file mode 100644
index 0000000000..43d6c5e5e4
--- /dev/null
+++ b/contrib/calendar/os-macosx.factor
@@ -0,0 +1,48 @@
+IN: calendar
+USING: alien arrays compiler errors kernel math ;
+
+TYPEDEF: uint time_t
+
+BEGIN-STRUCT: tm
+    FIELD: int sec     ! Seconds: 0-59 (K&R says 0-61?)
+    FIELD: int min     ! Minutes: 0-59
+    FIELD: int hour    ! Hours since midnight: 0-23
+    FIELD: int mday    ! Day of the month: 1-31
+    FIELD: int mon     ! Months *since* january: 0-11
+    FIELD: int year    ! Years since 1900
+    FIELD: int wday    ! Days since Sunday (0-6)
+    FIELD: int yday    ! Days since Jan. 1: 0-365
+    FIELD: int isdst   ! +1 Daylight Savings Time, 0 No DST,
+    FIELD: long gmtoff
+    FIELD: char* zone
+END-STRUCT
+
+FUNCTION: time_t time ( time_t* t ) ;
+FUNCTION: tm* localtime ( time_t* clock ) ;
+FUNCTION: size_t strftime ( char* buf, size_t maxsize, char* format, tm* timeptr ) ;
+
+BEGIN-STRUCT: t
+    FIELD: long tv_sec
+    FIELD: long tv_usec
+END-STRUCT
+
+BEGIN-STRUCT: tz
+    FIELD: int tz_minuteswest
+    FIELD: int tz_dsttime
+END-STRUCT
+
+FUNCTION: int gettimeofday ( t* timeval, tz* timezone ) ;
+
+: machine-gmt-offset
+    "t" <c-object> "tz" <c-object> 2dup gettimeofday
+    zero? [ nip tz-tz_minuteswest 60 / neg ] [ 2drop 0 ] if ;
+
+\ gettimeofday compile
+
+
+: timezone-name
+    get-time tm-zone ;
+
+: gmt-offset
+    get-time tm-gmtoff 3600 / ;
+
diff --git a/contrib/calendar/os-unix.factor b/contrib/calendar/os-unix.factor
index 2d37f2df92..e8334f1c75 100644
--- a/contrib/calendar/os-unix.factor
+++ b/contrib/calendar/os-unix.factor
@@ -1,4 +1,32 @@
 IN: calendar
-USING: alien ;
+USING: alien arrays compiler errors kernel math ;
 
 TYPEDEF: uint time_t
+BEGIN-STRUCT: t
+    FIELD: long tv_sec
+    FIELD: long tv_usec
+END-STRUCT
+
+FUNCTION: time_t time ( time_t* t ) ;
+FUNCTION: tm* localtime ( time_t* clock ) ;
+
+: get-time
+    f time <uint> localtime ;
+
+
+
+
+
+
+
+! BEGIN-STRUCT: tz
+    ! FIELD: int tz_minuteswest
+    ! FIELD: int tz_dsttime
+! END-STRUCT
+
+! FUNCTION: int gettimeofday ( t* timeval, tz* timezone ) ;
+
+! : machine-gmt-offset
+    ! "t" <c-object> "tz" <c-object> 2dup gettimeofday
+    ! zero? [ nip tz-tz_minuteswest 60 / neg ] [ 2drop 0 ] if ;
+