diff --git a/src/common.ts b/src/common.ts
index d2c197f..968c159 100644
--- a/src/common.ts
+++ b/src/common.ts
@@ -98,8 +98,12 @@ export abstract class Reactive<A, C extends Child> implements Child {
   subscribe(callback: (a: A) => void): PushOnlyObserver<A> {
     return new PushOnlyObserver(callback, this);
   }
-  observe(push: (a: A) => void, handlePulling: PullHandler): CbObserver<A> {
-    return new CbObserver(push, handlePulling, this);
+  observe(
+    push: (a: A) => void,
+    handlePulling: PullHandler,
+    t: Time = tick()
+  ): CbObserver<A> {
+    return new CbObserver(push, handlePulling, t, this);
   }
   activate(t: number): void {
     let newState = State.Done;
@@ -127,9 +131,10 @@ export class CbObserver<A> implements BListener, SListener<A> {
   private endPulling: () => void;
   node: Node<CbObserver<A>> = new Node(this);
   constructor(
-    private callback: (a: A) => void,
-    private handlePulling: PullHandler,
-    private source: Parent<Child>
+    readonly callback: (a: A) => void,
+    readonly handlePulling: PullHandler,
+    private time: Time,
+    readonly source: Parent<Child>
   ) {
     source.addListener(this.node, tick());
     if (source.state === State.Pull) {
@@ -137,8 +142,11 @@ export class CbObserver<A> implements BListener, SListener<A> {
     } else if (isBehavior(source) && source.state === State.Push) {
       callback(source.last);
     }
+    this.time = undefined;
   }
-  pull(t: number = tick()): void {
+  pull(time: number): void {
+    const t =
+      time !== undefined ? time : this.time !== undefined ? this.time : tick();
     if (isBehavior(this.source) && this.source.state === State.Pull) {
       this.source.pull(t);
       this.callback(this.source.last);
diff --git a/src/index.ts b/src/index.ts
index 22d9ed2..eb27cd5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,20 +1,7 @@
 import { Now, MapNowTuple, InstantRun, instant, sample } from "./now";
-import {
-  Behavior,
-  SinkBehavior,
-  MapBehaviorTuple,
-  AccumPair,
-  accum,
-  accumCombine,
-  stepper,
-  when,
-  toggle,
-  switcher,
-  freezeAt
-} from "./behavior";
-import { Stream, SinkStream, scan, shift } from "./stream";
+import { Behavior, SinkBehavior, MapBehaviorTuple } from "./behavior";
+import { Stream, SinkStream } from "./stream";
 import { Future, MapFutureTuple } from "./future";
-import { integrate } from "./time";
 
 export * from "./common";
 export * from "./now";
@@ -24,6 +11,7 @@ export * from "./future";
 export * from "./time";
 export * from "./placeholder";
 export * from "./animation";
+export * from "./clock";
 
 /**
  * Map a function over a behavior or stream. This means that if at some point in
@@ -65,7 +53,7 @@ export function push<A>(a: A, sink: SinkBehavior<A> | SinkStream<A>): void {
   sink.push(a);
 }
 
-export function combine<A>(...streams: Future<A>[]): Future<A>;
+export function combine<A>(...futures: Future<A>[]): Future<A>;
 export function combine<A>(...streams: Stream<A>[]): Stream<A>;
 export function combine<A>(
   ...values: Future<A>[] | Stream<A>[]
diff --git a/test/behavior.ts b/test/behavior.ts
index 42043b8..e283cc6 100644
--- a/test/behavior.ts
+++ b/test/behavior.ts
@@ -119,6 +119,22 @@ describe("behavior", () => {
       assert.deepEqual(spy.args, [[1], [2], [3]]);
     });
   });
+  describe("observe", () => {
+    it("samples in same timestamp", () => {
+      const f = jest.fn(() => 0);
+      const b = fromFunction(f);
+      let result = -1;
+      b.observe(
+        (n) => result,
+        (pull) => {
+          pull();
+          return () => {};
+        },
+        3
+      );
+      expect(f.mock.calls).toEqual([[3]]);
+    });
+  });
   describe("fromFunction", () => {
     it("pulls from time varying functions", () => {
       let time = 0;
@@ -241,18 +257,20 @@ describe("behavior", () => {
         const numE = H.fromFunction(() => n);
         const applied = H.ap(fnB, numE);
         const cb = spy();
-        applied.observe(cb, (pull) => {
-          pull();
-          push(add(2), fnB);
-          pull();
-          n = 4;
-          pull();
-          push(double, fnB);
-          pull();
-          n = 8;
-          pull();
+        let pull: () => void;
+        applied.observe(cb, (pull_) => {
+          pull = pull_;
           return () => {};
         });
+        pull();
+        push(add(2), fnB);
+        pull();
+        n = 4;
+        pull();
+        push(double, fnB);
+        pull();
+        n = 8;
+        pull();
         assert.deepEqual(cb.args, [[6], [3], [6], [8], [16]]);
       });
     });