     unix-1970 time+ ; inline
 
 : timestamp>unix-time ( timestamp -- seconds )
-    unix-1970 time- second>> ; inline
+    unix-1970 (time-) ; inline
 
 : unix-time>timestamp ( seconds -- timestamp )
-    seconds since-1970 ; inline
+    [ unix-1970 ] dip +second ; inline
 
 {
     { [ os unix? ] [ "calendar.unix" ] }

    1970 <year-gmt> ; inline

: millis>timestamp ( x -- timestamp )
    [ unix-1970 ] dip milliseconds time+ ;

: timestamp>millis ( timestamp -- n )
    unix-1970 (time-) 1000 * >integer ;

: micros>timestamp ( x -- timestamp )
    [ unix-1970 ] dip microseconds time+ ;

: timestamp>micros ( timestamp -- n )
    unix-1970 (time-) 1000000 * >integer ;

: now ( -- timestamp ) gmt >local-time ;
: hence ( duration -- timestamp ) now swap time+ ;
: ago ( duration -- timestamp ) now swap time- ;

: zeller-congruence ( year month day -- n )

: before ( duration -- -duration )
    -1 time* ;

<PRIVATE

: -slots ( obj1 obj2 quot -- n obj1 obj2 )
    [ bi@ - ] curry 2keep ; inline

PRIVATE>

M: duration time-
    over timestamp? [
        before time+
    ] [
        [ year>> ] -slots
        [ month>> ] -slots
        [ day>> ] -slots
        [ hour>> ] -slots
        [ minute>> ] -slots
        [ second>> ] -slots
        2drop <duration>
    ] if ;

: <zero> ( -- timestamp )
    0 0 0 <date-gmt> ; inline
